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Alexander von Humboldt: „New Inquiries into the Laws which are observed in the Dirstribution of Vegetable Forms“, in: ders., Sämtliche Schriften digital, herausgegeben von Oliver Lubrich und Thomas Nehrlich, Universität Bern 2021. URL: <https://humboldt.unibe.ch/text/1821-Nouvelles_recherches_sur-08> [abgerufen am 17.04.2024].

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Titel New Inquiries into the Laws which are observed in the Dirstribution of Vegetable Forms
Jahr 1822
Ort Edinburgh
Nachweis
in: The Edinburgh Philosophical Journal 6:12 (April 1822), S. 273–289; 7:13 (Juli 1822), S. 47–55.
Sprache Englisch
Typografischer Befund Antiqua; Auszeichnung: Kursivierung, Kapitälchen; Fußnoten mit Asterisken; Schmuck: Initialen; Tabellensatz.
Identifikation
Textnummer Druckausgabe: IV.13
Dateiname: 1821-Nouvelles_recherches_sur-08
Statistiken
Seitenanzahl: 26
Spaltenanzahl: 6
Zeichenanzahl: 55431

Weitere Fassungen
Nouvelles Recherches sur les lois que l’on observe dans la distribution des formes végétales (Paris, 1821, Französisch)
Neue Untersuchungen über die Gesetze, welche man in der Vertheilung der Pflanzenformen bemerkt (Jena; Leipzig, 1821, Deutsch)
Natural history (Liverpool, 1822, Englisch)
Natural History (London, 1822, Englisch)
Natural History (Paris, 1822, Englisch)
Natural History (London, 1822, Englisch)
Natural History (London, 1822, Englisch)
New Inquiries into the Laws which are observed in the Dirstribution of Vegetable Forms (Edinburgh, 1822, Englisch)
Natural History (London, 1822, Englisch)
Natural History I / Histoire naturelle I (Moskau, 1823, Englisch; Französisch)
|273|

New Inquiries into the Laws which are observed inthe Distribution of Vegetable Forms. By Baron Alexan-der Humboldt *.

The numerical proportions of vegetable forms may be view-ed in two perfectly distinct lights. If we consider plants, group-ed together in natural families, without having regard to theirgeographical distribution, we enquire what are the types of or-ganization, according to which the greatest number of speciesare formed. Are there more Glumaceæ than Compositæ on theglobe? Do these two tribes of vegetables constitute togetherthe fourth part of Phænogamous plants? What is the pro-portion of Monocotyledones to the Dicotyledones? These arequestions of general Phytology—of the sciences which examinethe organization and mutual connection of vegetables. If weview the species which we associate according to the analogy oftheir form, not in an abstract manner, but with regard to theirclimacteric relations, or their distribution over the surface ofthe globe, the questions which arise afford an interest highlyvaried. What are the families of plants which predominateover the other phænogamous vegetables more within the tor-rid zone than under the polar circle? Are the Compositæ morenumerous, either in the same geographical latitude, or on thesame isothermal band, in the new Continent than in the old?Do the types which predominate less in advancing from the
* A separate copy of this memoir was sent to us by the author for insertion inour Journal, through Dr Marcet.
|274| equator to the pole, follow the same law of decrease, in propor-tion as they rise toward the summit of the equatorial mountains?Do not the mutual proportions of families vary, on isothermallines of the same denomination, in the temperate zones, to thenorth and to the south of the equator? These questions belongto the geography of plants, properly so called: they are connectedwith the most important problems belonging to meteorology andthe natural history of the globe in general. Upon the prepon-derance of certain families of plants, depends also the characterof the landscape, the aspect of a country, whether of a beautifulor majestic nature. The abundance of the Gramineæ, whichform vast savannahs, and that of the Palms or the Coniferæ,are much influenced by the social state of the people, by theirmanners, and by the more or less perfect development of theeconomical arts.
In considering the geographical distribution of forms, we mayattend to species, to genera, and to natural families, (Humboldt,Proleg. in Nov. Gen. vol. i. pp. xiii. li. & 33.). Often a singlespecies of plants, especially among those which I have namedsocial plants, covers a vast extent of country. Of this kind, inthe north, are the heaths and forests of pines; in equinoctialAmerica, the associations of Cactus, Croton, Bambusa, andBrathys of the same species. It is curious to examine the pro-portions of organic multiplication and development. We maydemand what species in a given zone produces the greatestnumber of individuals;—we may point out the families to whichin different climates belong the species which predominates overthe others. Our imagination is peculiarly struck with the pre-ponderance of certain plants, which we consider, on account oftheir easy reproduction, and the great number of individualswhich present the same specific characters, as the more commonplants of this or that zone. In a northern region, where theCompositæ and the Ferns are to the phænogamous plants inthe proportion of 1:13, and of 1:25, (that is to say, where wefind these proportions on dividing the total number of the phæ-nogamous plants by the number of the species of the Compo-sitæ and Ferns,) a single species of Fern may occupy ten timesas much space as the whole species of Compositæ together. Inthis case, the Ferns predominate over the Compositæ by the|275| mass,—by the number of individuals belonging to the samespecies of Pteris or of Polypodium; but they do not predominate,if we compare with the total sum of the species of phænoga-mous plants the different forms which compose the two groupsof Ferns and Compositæ. As the multiplication of all the spe-cies does not follow the same laws, since they do not all producethe same number of individuals, the quotient obtained in di-viding the total number of phænogamous plants by the num-ber of species of different families, does not of itself decide theaspect, I might almost say kind of monotony of nature in thedifferent regions of the globe. If the traveller is struck withthe frequent repetition of the same species,—with the sight ofthose which predominate by their mass,—he is not less so withthe paucity of individuals of some other species useful to man.In the countries where the Rubiaceæ, the Leguminosæ, or theTerebinthaceæ, compose the forests, we are surprised to see howrare are the trees of certain species of Cinchona, Hæmatoxylon,and the Balsamiferæ. In turning our attention to species, we may also, withouthaving regard to their multiplication, and to the greater orsmaller number of individuals, compare in each zone, in an ab-solute manner, the species which belong to different families.This interesting comparison has been made in the great work ofM. Decandolle, (Regni Vegetabilis Systema Naturæ, vol. i.p. 128. 396. 439. 464. 510.). M. Kunth has attempted it withmore than 3300 Compositæ already known up to the presentday, (Nova Genera, vol. iv. p. 238). It does not point outwhat family predominates in the same degree above the otherindigenous phænogamous plants, either by the mass of in-dividuals, or by the number of species; but it presents thenumerical proportions between the species of the same familybelonging to a different country. The results of this methodare generally more precise, because they are obtained withoutvaluing the total mass of phænogamous plants, after beingfreed with care from the study of each isolated family. Theforms which are the most varied, the Ferns, for example, arefound under the tropics: it is in the mountainous, temperate,humid and shady parts of the equatorial regions, that the familyof Ferns produces the greatest number of species. In the tem-|276| perate zone, there are not so many as under the tropics: theirabsolute number still diminishes as we advance toward the pole,but since the cold region, for example Lapland, produces spe-cies of Ferns which resist the cold better than the great massof phænogamous plants, the Ferns, by the number of spe-cies, predominate more over the other plants in Lapland than inFrance or Germany. The numerical proportions presented inthe table which I have published in my Prolegomena de Distri-butione Geographica Plantarum, and which appears again hereperfected by the great labours of Mr Robert Brown, differ en-tirely from the proportions given by an absolute comparison ofthe species which grow in the different zones. The variationwhich we observe in proceeding from the equator to the poles isnot consequently the same in the result of the two methods. Inthis, two of the fractions used by Mr Brown and myself are va-riable, since, in changing the latitude, or rather the isothermalzone, the total number of phænogamous plants is not seen tovary in the same proportion as the number of species whichconstitute the same family. When from species or individuals of the same form whichare reproduced according to constant laws, we pass to divisionsof the natural method, we may turn our attention to genera, tofamilies, or to sections still more general. There are some ge-nera and some families which belong exclusively to certain zones,to a particular association of climacteric conditions; but there is agreat number of genera and of families which have representativesin all zones, and at all heights. The first researches which havebeen made regarding the geographical distribution of forms,those of M. Treviranus, published in his ingenious work onBiology, (vol. ii. p. 47. 63. 83. 129.), have for their object thedispersion of genera over the globe. That method is less pro-per for presenting general results than this, which compares thenumber of species of each family, or the large groups of thesame family, with the total mass of phænogamous plants. Inthe frigid zone, the variety of generie forms does not diminishin the same degree as the variety of species: we find more ge-nera, with a smaller number of species, (Decandolle, ThéorieElément. p. 190.; Humboldt, Nova Gen. vol. i. p. xvii. & l.).It is nearly the same on the summit of the lofty mountains,|277| which receive colonists of a great number of genera, which wesuppose to belong exclusively to the vegetation of the plains. I have deemed it necessary to show the different points ofview from which the laws of the distribution of vegetables maybe seen. It is in confounding them that we think the contra-dictions are to be found, which are not otherwise than appa-rent, and which are erroneously attributed to the uncertainty ofobservations. (Berliner Jahrbücher der Gewächskunde, Bd. i.p. 18. 21. 30.) When the following expressions are used:“this form or this family loses itself toward the frigid zone;““it has its true native country in such and such a parallel;““it is a southern form;” “it abounds in the temperate zone;”we must expressly mention, if we consider the absolute numberof species, the increase or decrease of their absolute frequencywith the latitudes, or if we speak of families which predominatein the same degree over the rest of the phænogamous plants.These expressions are correct: they afford a precise significa-tion, if we distinguish the different methods according to whichwe consider the variety of forms. The Island of Cuba (to usean analogous case taken from political economy) contains amuch greater number of individuals of the African than of theMartinique race; and yet the mass of these individuals predo-minates much more over the number of whites in this latterisland than in that of Cuba. The rapid progress which the geography of plants has madewithin these twelve years, by the united labours of MessrsBrown, Wahlenberg, Decandolle, Leopold de Buch, Parrot, Ra-mond, Schouw and Hornemann, are owing in a great measure tothe advantages of the natural method of M. de Jussieu. In fol-lowing, I shall not say the artificial classifications of the sexualsystem, but the families founded upon vague and erroneousprinciples, ( Dumosæ, Corydales, Oleraceæ,) we no longer per-ceive the great physical laws in the distribution of vegetableson the globe. It was Mr Robert Brown, who, in a celebratedmemoir on the vegetation of New Holland, first made knownthe true proportions between the great divisions of the vege-table kingdom, the Acotyledonous, Monocotyledonous, andDicotyledonous plants. (Brown, in Flinders’ Voyage to Terra|278| Australis, vol. ii. p. 538; and Observations systematic andgeographical on the Herbaries of the Congo, p. 3.) I madean attempt, in 1815, to pursue this kind of research, in extend-ing it to the different orders or natural families. The naturalhistory of the globe is, in its numerical elements, like the sys-tem of the world, and can be brought to perfection only by thejoint efforts of botanical travellers, to discover the true laws ofthe distribution of vegetables. The collection of facts is not ofitself sufficient: in order to obtain the most accurate approxi-mations, (and we do not pretend to give any thing but approxi-mations,) the different circumstances under which the observa-tions have been made must be discussed. I think with MrBrown, that we ought to prefer in general to calculations madeupon incomplete lists of all the plants published, the examplestaken from countries of considerable extent, and whose Flora iswell known, such as France, England, Germany, and Lapland.It would be desirable to have still a complete Flora of two coun-tries of 20,000 square leagues, destitute of lofty mountains andof platforms, and situated between the tropics in the Old and inthe New Worlds. Until this shall be accomplished, we must becontented with the great herbaries formed by travellers, whohave resided for some time in the two hemispheres. The habi-tations of plants are so vaguely and incorrectly pointed out, inthe vast compilations known under the names of Systema Vege-tabilium, and Species Plantarum, that it would be very dange-rous to use them in an absolute manner. I have not employedthese lists otherwise than in a subsidiary manner, to controland modify a little the results obtained by the Floras and thepartial herbaries. The number of equinoctial plants which M.Bonpland and I have brought to Europe, and of which ourlearned colleague M. Kunth will have soon finished the publi-cation, is perhaps numerically greater than any of the herbariesformed between the tropics; but it is composed of the vegetablesof the plains and elevated platforms of the Andes. The al-pine plants are even much more considerable than in the Florasof France, of England, and of the Indies, which associate alsothe productions of different climates belonging to the same lati-tude. In France, the number of species which vegetate exclu-sively at above 500 toises of height, does not appear to be more|279| than \( \frac{1}{9} \)th of the entire mass of phænogamous plants. (Decan-dolle, in the Mem. de Arcueil, vol. iii. p. 295.). It will be useful to consider at a future period the vegetationof the tropics and that of the temperate region between the pa-rallels of 40° and 50°, according to two different methods, eitherin searching the numerical proportions in the whole of the plainsand the mountains, which nature presents over a great extent ofcountry, or in determining these proportions in the plains aloneof the temperate zone and of the torrid zone. As our herbariesare the only ones that point out, according to barometricalmeasurement, in more than 4000 plants of the equinoctial re-gion, the height of each station above the level of the sea, thenumerical proportions of the table which I have already pub-lished may be rectified, when our work, the Nova Genera,shall be finished, by taking away from the 4000 phænogamousplants which M. Kunth has employed in this work (Prolegom.p. 16.), the plants which grow at above 1000 toises, and by di-viding the total number of plants which are not alpine, of eachfamily, by that of plants which live in the cold and temperateregions of equinoctial America. This mode of proceedingshould affect more, as we shall show by and bye, the familieswhich abound in alpine species, for example, the Gramineæ andthe Compositæ. At 1000 toises of elevation, the mean tempe-rature of the air is still, on the back of the equatorial Andes,17° centigr., which is equal to that of the month of July at Pa-ris. Although on the platform of the Cordilleras, we find thesame annual temperature as in the high latitudes, (because theisothermal line of 8°, for example, is the track marked in theplains by the intersection of the isothermal surface of 8°, withthe surface of the earth’s spheroid,) it is not too much to gene-ralise these analogies of the temperate climates of the equatorialmountains, with the low regions of the circumpolar zone. Theseanalogies are not so great as might be thought; they are modi-fied by the influence of the partial distribution of the heat inthe different parts of the year. (Proleg. p. 54., and my Mé-moire sur les Lignes Isothermes *, p. 137.) The quotients do
* A translation of this valuable Memoir will be found in this Journal, vol. III.pp. 1, 256.; IV. pp. 23, 262.; V. p. 28.
|280| not change, however, in ascending from the plains toward themountains, in the same manner as they change in approachingthe pole: this is the case with the Monocotyledones, consideredin a general view, as well as with the Ferns and Compositæ.(Proleg. p. 51. and 52.; Brown on Congo, p. 5.)
It may further be remarked, that the development of vege-tables of different families, and the distribution of forms, dependnot on isothermal latitudes, nor on geographical latitudes alone;but that the quotients are not always similar on the same iso-thermal line of the temperate zone, in the plains of Americaand of the Old Continent. There exists, under the tropies, avery remarkable difference between America, India, and thewest coasts of Africa. The distribution of organic beings onthe globe, depends not only on very complicated climatic cir-cumstances, but also on geological causes, with which we are en-tirely unacquainted, because they are connected with the ori-ginal state of our planet. The great Pachydermata are want-ing at the present day in the New World, although we find themstill in abundance in analogous climates, in Africa, and in Asia.In the equinoctial zone of Africa, the family of palms is farfrom numerous, compared with the great number of species ofequinoctial America. These differences, far from deterring usfrom the scrutiny of the laws of nature, ought to excite usto study these laws in all their complications. The lines ofequal heat are not parallel to the equator. They have, as Ihave tried to prove elsewhere, convex summits, and concavesummits, which are distributed with great regularity over theglobe, and form different systems along the eastern and wes-tern coasts of the two worlds, in the centre of continents, and inthe neighbourhood of the ocean. It is probable, that whenphilosophical botanists have travelled over a larger extent ofthe globe, we shall find, that often the lines of the maximaof agroupment (the lines taken from the points where thefractions are reduced to the smallest denominator,) becomeisothermal lines. In dividing the globe by longitudinal bandscomprehended between two meridians, and in comparing thenumerical proportions under the same isothermal latitudes, weperceive the existence of different systems of agroupment. Wecan already, with the actual state of our knowledge, distinguish|281| four systems of vegetation, those of the New Continent, of Wes-tern Africa, of India, and of New Holland. Since, notwith-standing the regular increase of the mean heat from the pole tothe equator, the maximum of heat is not identical in the diffe-rent regions at different degrees of longitude, there exist alsoplaces where certain families attain a more perfect developmentthan at any other: this is the case with the family of Composi-tæ in the temperate region of North America, and especially atthe southern extremity of Africa. These partial accumulationsdetermine the physiognomy of the vegetation, and are what wecall vaguely the characteristic features of the landscape. In the whole temperate zone, the Glumaceæ and Compositæform together more than the fourth part of the phænogamousplants. We find, from the same inquiries, that the forms oforganised beings have a mutual dependence. The unity ofnature is such, that the forms are universally limited accordingto constant and immutable laws. When we know at any pointof the globe the number of species which a great family pre-sents, (for example, that of the Glumaceæ, the Compositæ, orthe Leguminosæ,) we can estimate with much probability boththe total number of phænogamous plants, and the number ofspecies which compose the other vegetable families. It is thus,that, on knowing the number of Cyperaceæ or of Compositæ inthe temperate zone, we can form an estimate of that of theGramineæ or Leguminosæ. These estimates enable us to see inwhat tribes of vegetables the Floras of a country are still defi-cient: they are so far from being uncertain, as to enable us toavoid confounding the quotients which belong to the differentsystems of vegetables. The labour which I have bestowedupon plants, will no doubt one day be applied with success tothe different classes of vertebral animals. In the temperatezones, there are nearly five times as many birds as mammalia,and the latter increase much less toward the equator than thebirds and reptiles. The geography of plants may be considered as a part of thenatural history of the globe. If the laws which nature has fol-lowed in the distribution of vegetable forms, should prove to bemore complicated than they appear at first sight, still, we oughtnot on this account to be deterred from submitting them to ac-|282| curate investigation. We do not relinquish the tracing of a map,when we perceive the sinuosities of rivers, and the irregular formof coasts. The laws of magnetism become intelligible to himwho has commenced with tracing the lines of equal inclination anddeclination, and who has compared a great number of observations,which, at first sight, might seem contradictory. He who thinksthat it is not yet time to search the numerical elements of thegeography of plants, forgets the progressive march by whichthe physical sciences have elevated themselves to determinateresults. In examining a complicated phenomenon, we com-mence with a general scrutiny of the circumstances by which itis determined or modified; but, before discovering certain pro-portions, we find, that the first results to which we attend, arenot sufficiently free from local influence: it is then that we mo-dify and correct the numerical elements, and discover theregularity in the very effects of partial disturbances. Criti-cism exercises itself on whatever has been prematurely announ-ced as a general result; and the spirit of criticism once excited,becomes favourable to the investigation of truth, and acceleratesthe progress of human knowledge. Acotyledones. Cryptogamous plants (fungi, lichens, mos-ses, and ferns); Agames celluleuses et vasculaires of M. De-candolle. On uniting the plants of the plains with those ofthe mountains, we have found them to be under the tropics \( \frac{1}{9} \);but their number ought to be much greater. Mr Brown hasrendered it very probable, that, in the torrid zone, the propor-tion is in the plains \( \frac{1}{15} \), on the mountains \( \frac{1}{5} \) *. (Congo, p. 5.)In the temperate zone, the agamous plants are generally to thephænogamous as 1:2; in the frigid zone they attain the samenumber, and often exceed it considerably. On dividing the agamous plants into three groups, we observethat the ferns are more frequent (the denominator of the frac-tion being less) in the frigid zone than in the temperate zone,(Berl. Jahrb., bd. i. p. 32.), and the lichens and mosses also in-
* In this article, the fractions \( \frac{1}{9} \), \( \frac{1}{15} \), \( \frac{1}{5} \), indicate the proportions betweenthe species of a family and the total number of Phænogamous plants whichvegetate in the same country. The abbreviations Trop. Temp. Frig., signifyTropies or Torrid Zone, Temperate Zone, Frigid Zone.
|283| crease towards the frigid zone. The geographical distributionof ferns depends upon the union of the local circumstances ofshade, humidity, and moderate heat. Their maximum (that isto say, the place where the denominator of the normal fractionof a group becomes the least possible,) is found in the moun-tainous parts of the tropics, particularly in islands of small ex-tent, where the proportion rises to \( frac{1}{3} \), and upwards. When theplains and mountains were not separated, Mr Brown found theferns of the torrid zone to be \( \frac{1}{20} \). In Arabia, India, New Hol-land, and Western Africa, (between the tropics,) they are \( \frac{1}{26} \):our herbaries of America do not give more than \( \frac{1}{38} \); but theferns are rare in the great valleys and on the dry platforms ofthe Andes, where we were forced to remain a long time.(Congo, p. 43., and Nova gen., vol. i. p. 33.) In the tempe-rate zone, the ferns are \( \frac{1}{70} \); in France, \( \frac{1}{75} \); in Germany, ac-cording to late inquiries, \( \frac{1}{71} \). (Berl. Jahrb., b. i. p. 26.) Thegroup of ferns is extremely rare on the Atlas mountains, andalmost completely disappears in Egypt. In the frigid zone,the ferns appear to rise to \( \frac{1}{25} \).
Monocotyledones. The denominator becomes progres-sively smaller in proceeding from the equator toward the 62ddegree of North Latitude; it increases again in the regions stillfarther north, on the coast of Greenland, where the Gramineæare very scanty. (Congo, p. 10.) In the different parts of thetropics, the proportion varies from \( \frac{1}{5} \) to \( \frac{1}{6} \). In 3880 phæno-gamous plants of equinoctial America, found by M. Bonplandand me, in flower and in fruit, there are 654 monoctyledonous,and 3226 dicotyledonous; hence the great division of the Mo-nocotyledones would be \( \frac{1}{6} \) of the phænogamous plants. Ac-cording to Mr Brown, the proportion in the Old Continent (inIndia, equinoctial Africa, and New Holland,) is \( \frac{1}{5} \); in thetemperate zone we find \( \frac{1}{4} \). (France, 1:4\( \frac{5}{5} \); Germany, 1:4\( \frac{1}{2} \);North America, according to Pursh, 1:4\( \frac{1}{2} \); Kingdom of Na-ples, 1:4\( \frac{1}{5} \); Switzerland, 1:4\( \frac{1}{4} \); British Isles, 1:3\( \frac{5}{4} \)); inthe frigid zone, \( frac{1}{3} \). Glumaceæ. (The three families of Junceæ, Cyperaceæ,and Gramineæ, united). = Trop., \( \frac{1}{11} \). Temp., \( \frac{1}{8} \). Frig., \( \frac{1}{4} \). |284| The increase toward the north is owing to the Junceæ andCyperaceæ being very rare compared with the other Phæno-gamous plants, in the temperate and torrid zones. On com-paring the species belonging to the three families, we find thatthe Gramineæ, the Cyperaceæ, and the Junceæ, are under thetropics, as 25, 7, 1; in the temperate region of the Old Conti-nent, as 7, 5, 1; in the polar circle, as 2\( \frac{2}{5} \), 2\( \frac{5}{5} \), 1. In Laplandthe Gramineæ and Cyperaceæ are equal: toward the equatorthe Cyperaceæ and Junceæ diminish much more than the Gra-mineæ; the junceal form disappears almost entirely under thetropics, (Nova Gen. vol. i. p. 240.).
  • Junceæ alone. = Trop., \( \frac{1}{400} \). Temp., \( \frac{1}{90} \). Frig., \( \frac{1}{25} \),(Germany, \( \frac{1}{94} \); France, \( \frac{1}{86} \).)
  • Cyperaceæ alone. = Trop. America, nearly \( \frac{1}{57} \); WesternAfrica, \( \frac{1}{18} \); India, \( \frac{1}{25} \); New Holland, \( \frac{1}{14} \). (Congo, p. 9).Temp., probably \( \frac{1}{20} \). (Germany, \( \frac{1}{16} \); France, according tothe works of M. Decandolle, \( \frac{1}{27} \); Denmark, \( \frac{1}{16} \).) Frig. \( \frac{1}{9} \).This is the proportion found in Lapland, and as far as Kamt-schatka.
  • Gramineæ alone. Trop. I have allowed as much as \( \frac{1}{15} \).Mr Brown found in Western Africa, \( \frac{1}{12} \); in India, \( \frac{1}{12} \). (Con-go, p. 41.) M. Hornemann fixed this part of Africa at \( \frac{1}{10} \).(De Indole Plant. Guineensium, 1819, p. 10.) Temp. Ger-many, \( \frac{1}{15} \); France, \( \frac{1}{15} \). Frig. \( \frac{1}{10} \).
Compositæ. On blending the plants of the plains with thoseof the mountains, we have found in equinoctial America \( \frac{1}{6} \) and\( \frac{1}{7} \); but, of 534 Compositæ of our herbaries, there are only 94which grow to 500 toises above the plains, (the height at whichthe mean temperature is still 21°.8; equal to that of Cairo, ofAlgiers, and of the Island of Madeira.) From the equatorialplains to 1000 toises of height (where we have still the meantemperature of Naples), we have collected 265 Compositæ.This last result gives the proportion of Compositæ, in the re-gions of equinoctial America, beneath 1000 toises, from \( \frac{1}{9} \) to \( \frac{1}{10} \).This result is very remarkable, because it proves, that between|285| the tropics in the lowest and warmest region of the New Conti-nent, there are fewer Compositæ, in the subalpine and tempe-rate regions more, than under the same circumstances in the OldWorld. Mr Brown found on the Rio-Congo, and in Sierra-Leone, \( \frac{1}{25} \); in India and New Holland \( \frac{1}{16} \). (Congo, p. 26;Nova Gen. vol. iv. p. 239.) In the temperate zone, the Com-positæ are in America, \( \frac{1}{6} \), (this is probably also in equinoctialAmerica the proportion of the Compositæ of the highest moun-tains to the whole mass of alpine phænogamous plants); atthe Cape of Good Hope, \( \frac{1}{5} \); in France, \( \frac{1}{7} \) (correctly \( \frac{2}{15} \)); inGermany \( \frac{1}{8} \). Under the frigid zone the Compositæ are, in Lap-land, \( \frac{1}{13} \); in Kamtschatka, \( \frac{1}{13} \). (Hornemann, p. 18.; Berl.Jahrb. b. i. p. 29.)
  • Leguminosæ. = Trop. America, \( \frac{1}{12} \); India, \( \frac{1}{9} \); New Hol-land, \( \frac{1}{9} \); Western Africa, \( \frac{1}{8} \), (Congo, p. 10.) Temp. France,\( \frac{1}{16} \); Germany, \( \frac{1}{20} \); North America, \( \frac{1}{19} \); Siberia, \( \frac{1}{14} \), (Berl.Jahrb. b. i. p. 22.) Frig. \( \frac{1}{35} \).
  • Labiatæ. = Trop. \( \frac{1}{40} \). Temp. North America, \( \frac{1}{40} \); Ger-many, \( \frac{1}{26} \); France, \( \frac{1}{24} \). Frig. \( \frac{1}{70} \). The rarity of Labiatæ andCruciferæ in the temperate zone of the New Continent is a veryremarkable phenomenon.
  • Malvaceæ. = Trop. America, \( \frac{1}{47} \); India and WesternAfrica, \( \frac{1}{54} \), (Congo, p. 9.); on the coast of Guinea alone, \( \frac{1}{20} \),(Hornemann, p. 20.) Temp. \( \frac{1}{200} \). Frig. 0.
  • Cruciferæ. Almost wanting under the tropics, on takingaway the mountains to within from 1200 to 1700 toises. (NovaGen. p. 16.) France, \( \frac{1}{19} \); Germany, \( \frac{1}{18} \); North America, \( \frac{1}{62} \).
Rubiaceæ. Without dividing the family into sections, wefind beneath the tropics, in America, \( \frac{1}{29} \); in Western Africa,\( \frac{1}{14} \): under the temperate zone in Germany, \( \frac{1}{70} \); in France,\( \frac{1}{73} \): under the frigid zone, in Lapland, \( \frac{1}{80} \). Mr Brown sepa-rates the great family of Rubiaceæ into two groups, which pre-sent very distinct climatic proportions. The group of Stel-latæ without interposed stipules, belong chiefly to the temperate|286| zone: it almost disappears between the tropics, excepting at thesummit of the mountains. The group of Rubiaceæ with oppo-site leaves and stipules, belong very peculiarly to the equinoc-tial region. M. Kunth has divided the great family of Rubia-ceæ into eight groups, one of which, that of the Coffeaceæ, formsin our herbaries a third part of the whole Rubiaceæ of equinoc-tial America. (Nov. Gen. vol. iii. p. 341.)
  • Euphorbiaceæ. = Trop. America, \( \frac{1}{35} \); India and NewHolland, \( \frac{1}{30} \); Western Africa, \( \frac{1}{28} \). (Congo, p. 25.) Temp.France, \( \frac{1}{70} \); Germany, \( \frac{1}{100} \). Frig. Lapland, \( \frac{1}{500} \).
  • Ericeæ and Rhododendra. = Trop. America, \( \frac{1}{130} \). Temp.France, \( \frac{1}{125} \); Germany, \( \frac{1}{90} \); North America, \( \frac{1}{36} \). Frig. Lap-land, \( \frac{1}{25} \).
  • Amentaceæ. = Trop. America, \( \frac{1}{800} \). Temp. France, \( \frac{1}{50} \);Germany, \( \frac{1}{40} \); North America, \( \frac{1}{25} \). Frig. Lapland, \( \frac{1}{20} \).
  • Umbelliferæ. = almost none under the tropics to theheight of 1200 toises; but, on taking both the plains and highmountains in equinoctial America, \( \frac{1}{100} \); under the temperatezone much more numerous in the Old than in the New Conti-nent. France, \( \frac{1}{34} \); North America, \( \frac{1}{57} \); Lapland, \( \frac{1}{60} \).
On comparing the two worlds, we find in general in the NewWorld, under the equatorial zone, fewer Cyperaceæ and Rubia-ceæ, and more Compositæ; under the temperate zone, fewerLabiatæ and Cruciferæ, and more Compositæ, Ericæ, and Amen-taceæ, than in the corresponding zones of the Old World. Thefamilies which increase from the equator toward the pole (ac-cording to the fractional method), are the Glumaceæ, the Eri-ceæ, and the Amentaceæ. The families which decrease fromthe pole toward the equator are the Leguminosæ, the Rubiaceæ,the Euphorbiaceæ, and the Malvaceæ. The families which ap-pear to attain the maximum under the temperate zone, are theCompositæ, the Labiatæ, the Umbelliferæ, and the Cruciferæ. I have thrown together the principal results of this work inone table; but I enjoin naturalists to have recourse to illustra-|287| tions of the several families, whenever any of the numbers seemdoubtful. The quotients of the tropics are modified in such amanner that they are proportioned to regions whose mean tem-perature is from 28° to 20°, (from the level of the sea to 750toises of height). The quotients of the temperate zone are adapt-ed to the central part of that zone, between 13° and 10° of meantemperature. In the frigid zone, the mean temperature is from0° to 1°. To this table of quotients or fractions, which indicatethe proportions of each family to the total mass of phænoga-mous plants, might be added another, in which the absolutenumber of species might be compared. We here present a frag-ment which comprehends only the temperate and frigid zones.
France. North America. Lapland.
Glumaceæ, ‒ ‒ 460 365 124
Compositæ, ‒ ‒ 490 454 38
Leguminosæ, ‒ ‒ 230 148 14
Cruciferæ, ‒ ‒ 190 46 22
Umbelliferæ, 170 50 9
Caryophylleæ, 165 40 29
Labiatæ, ‒ ‒ 149 78 7
Rhinantheæ, ‒ ‒ 147 79 17
Amentaceæ, ‒ ‒ 69 113 23
These absolute numbers are taken from the works of MessrsDecandolle, Pursh, and Wahlenberg. The mass of plants de-scribed in France is to that of North America in the proportionof 1\( \frac{1}{2} \):1; to that of Lapland in the proportion of 7:1 *.
* A series of additional observations on this subject, so highly interesting tothe philosophical botanist and the geologist, also by Baron Humboldt, will appearin our next Number.
|288|
Groups, founded on the Analogy ofForms. Proportions to the whole mass of Phænogamous Plants. Signs indi-cating thedirection ofIncrease.
Equatorial Zone,Lat. 0°—10°. Temperate Zone,Lat. 45°—52°. Frigid Zone,Lat. 67°—70°.
Agamous Plants,
  • Ferns,
  • Lichens,
  • Mosses,
  • Fungi,
Plains, ‒ ‒ ‒ \( \frac{1}{15} \)Mountains, ‒ ‒ ‒ \( \frac{1}{5} \) \( \frac{1}{2} \) \( \frac{1}{1} \)
Ferns alone. Country slightly Mountainous, \( \frac{1}{20} \)Country very Mountainous, \( frac{1}{3} \)\( \frac{1}{8} \) \( \frac{1}{70} \) \( \frac{1}{25} \) ← →
Monocotyledonous Plants. Old Continent, ‒ ‒ \( \frac{1}{5} \)New Continent, ‒ ‒ \( \frac{1}{6} \) \( \frac{1}{4} \) \( frac{1}{3} \)
Glumaceæ,
  • Junceæ,
  • Cyperaceæ,
  • Gramineæ,
\( \frac{1}{11} \) \( \frac{1}{8} \) \( \frac{1}{4} \)
Junceæ alone. \( \frac{1}{400} \) \( \frac{1}{90} \) \( \frac{1}{25} \)
Cyperaceæ alone. Old Continent, ‒ ‒ \( \frac{1}{22} \)New Continent, ‒ ‒ \( \frac{1}{50} \) \( \frac{1}{20} \) \( \frac{1}{9} \)
Gramineæ alone. \( \frac{1}{14} \) \( \frac{1}{12} \) \( \frac{1}{10} \)
Compositæ. Old Continent, ‒ ‒ \( \frac{1}{18} \)New Continent, ‒ ‒ \( \frac{1}{12} \) Old Continent, ‒ \( \frac{1}{8} \)New Continent, ‒ \( \frac{1}{5} \) \( \frac{1}{13} \) → ←
|289|
Leguminosæ. \( \frac{1}{10} \) \( \frac{1}{18} \) \( \frac{1}{35} \)
Rubiaceæ. Old Continent, ‒ ‒ \( \frac{1}{14} \)New Continent, ‒ ‒ 1 \( \frac{1}{60} \) \( \frac{1}{80} \)
Euphorbiaceæ. \( \frac{1}{32} \) \( \frac{1}{80} \) \( \frac{1}{500} \)
Labiatæ. \( \frac{1}{40} \) America, ‒ ‒ \( \frac{1}{40} \)Europe, ‒ ‒ \( \frac{1}{25} \) \( \frac{1}{70} \) → ←
Malvaceæ. \( \frac{1}{35} \) \( \frac{1}{200} \) 0
Ericeæ and Rhododendra. \( \frac{1}{130} \) Europe, ‒ ‒ \( \frac{1}{10} \)America, ‒ ‒ \( \frac{1}{36} \) \( \frac{1}{25} \)
Amentaceæ. \( \frac{1}{800} \) Europe, ‒ ‒ \( \frac{1}{45} \)America, ‒ ‒ \( \frac{1}{25} \) \( \frac{1}{20} \)
Umbelliferæ. \( \frac{1}{500} \) \( \frac{1}{40} \) \( \frac{1}{60} \) → ←
Cruciferæ. \( \frac{1}{800} \) Europe, ‒ ‒ \( \frac{1}{18} \)America, ‒ ‒ \( \frac{1}{60} \) \( \frac{1}{24} \) → ←
Explanation of the Signs: ↗ The denominator of the fraction diminished from the Equator toward the North Pole: ↙ The denomina-tor diminished toward the Equator: ← → The denominator diminished toward the Equator and toward the North Pole: → ← The denomina-tor diminished from the North Pole, and from the Equator toward the Temperate Zone.
|47|

New Inquiries into the Laws which are observed inthe Distribution of Vegetable Forms. By Baron Alexan-der Humboldt *. (Continued from Vol. VI. p. 289.)

It is with the distribution of organic beings as with all theother phenomena of the physical world. In the midst of appa-rent disorder, which seems to arise from the influence of amultitude of local causes, we discover the immutable laws ofNature, as soon as we cast our eyes over a great extent of coun-try, or employ a mass of facts with which the partial disturb-ances mutually agree. I have had the satisfaction to see thiswork completed by a minute examination made in Germany,England, Italy, and of late in Denmark. One of the great-est botanists of our times, and indeed of any age, Mr Ro-bert Brown, has compared each of the numerical results withthose given by the rich herbaries which he has had the oppor-tunity of consulting. Many of the numbers have been rectified,while the others have been confirmed by an agreement some-
* This continuation is taken from a Memoir read before the Academy ofSciences on the 19th February 1821.
|48| what unexpected. The mass of facts is increased by the verydesire of invalidating or corroborating the results to which Ihave applied myself. It is thus that, in the progress of the phy-sical sciences, general ideas, which at first have only been de-duced from a small number of facts, compel observers to mul-tiply the partial results. Enriched by these materials, profitingdaily by whatever truth or utility is contained in the most severecriticism of my works, I have been enabled to give to the nu-merical results of which the table of vegetable forms consists, adegree of exactness which I have not till now been able to at-tain. It is in the nature of these researches, that we are not ableto rectify the co-efficients otherwise than progressively, in propor-tion as the observations accumulate. I have attended here onlyto the general development of principles. As this kind of bo-tanical arithmetic demands more minute discussions of the pro-portions of each family of vegetables to the whole mass of phæ-nogamous plants, I have thrown together these discussions inthe notes which I have published separately *.
We may foresee, that the labour which I have bestowed onthe families of plants, will one day be applied with success tomost of the classes of vertebral animals. The immense collec-tions which are to be seen at Paris, in the Museum of NaturalHistory, show that we are already acquainted with nearly 56,000species of Plants, cryptogamous and phænogamous; 44,000 In-sects, 2500 Fishes; 700 Reptiles; 4000 Birds; and 500 speciesof Mammalia. Agreeably to the inquiries which M. Valenciennesand I have made, there exist in Europe alone nearly 80 Mam-malia, 400 Birds, and 30 Reptiles: it follows, that, in this nor-thern temperate zone, there are five times as many species ofBirds as of Mammalia, as there are (in Europe) five times asmany Compositæ as Amentaceæ and Coniferæ; five times as manyLeguminosæ as Orchideæ and Euphorbiaceæ. The beautifulcollections lately brought from the Cape of Good Hope by M.De Lalande prove, (if we compare them with the works ofMM. Temminik and Le Vaillant), that in that part of the sou-thern temperate zone, the Mammalia are to the Birds in the
* See Dictionnaire des Sciences Naturelles, arranged by the Professors of theGarden of Plants, vol. xviii. p. 423,—436.
|49| proportion of 1:4,3. Such an agreement between two oppositezones is abundantly striking. The Birds, and especially theReptiles, increase towards the equatorial zone in a much moreconsiderable degree than the Mammalia. According to the dis-coveries of M. Cuvier regarding fossil bones, we may be inducedto believe, that these proportions have not been the same in allages, and that, amid the ancient catastrophes of our planet, amuch greater number of Mammalia has been lost than of Birds.M. Latreille, in an excellent memoir on the Geographical Dis-tribution of Insects, has not compared the number of articulatedanimals with the number of plants, and with that of the diffe-rent classes of vertebral animals which inhabit the same cli-mates; but he has exhibited, in an interesting manner, a viewof the increase or diminution of the particular groups of insects,in advancing from the pole towards the equator. I pass overin silence the laborious researches of M. Illiger on the Geo-graphy of Birds *. The author has discussed the habitation ofupwards of 3800 species; but he has contented himself withviewing them according to their distribution among the five di-visions of the world,—a method by no means philosophical, andaltogether improper for investigating the influence of climateover the development of organized beings. All the continents,with the exception of Europe, extend from the temperate to theequatorial zone: the laws of Nature cannot, therefore, manifestthemselves, when we group the phenomena according to divi-sions which are arbitrary, and which depend, so to speak, sim-ply upon the difference of meridians. It is not my intention topush to a greater extent these considerations regarding the nu-merical proportions of animals of different classes. I am satis-fied with having called the attention of the learned to a branchof natural philosophy which has appeared to me very worthyof investigation. We conceive how, in a given space of coun-try, the individuals belonging to different tribes of plants andof animals may be numerically limited,—how, after an obsti-nate struggle, and long wavering, a state of equilibrium is esta-
* Memoirs of the Academy of Berlin for the years 1812 and 1813, p. 221,—237.
|50| blished, which results from the necessity of food, and the habi-tudes of life; but the causes which have limited the forms, arehidden under the impenetrable veil which conceals from oursight all that extends from the origin of things to the first de-velopment of organic life.
On examining in detail all that we already know regardingthe proportion of monocotyledonous to dicotyledonous plants,we find that the denominator becomes gradually smaller (andthis with a very great degree of regularity), in proceeding fromthe equator toward the 62d degree of N. Lat. It increasesprobably anew in regions still more northern, on the coast ofGreenland, where the Gramineæ have become very rare (Congo,p. 4.). The proportion varies from \( \frac{1}{5} \) to \( \frac{1}{6} \) in the different partsof the tropics. In upwards of 3880 phænogamous plants ofEquinoctial America, found by M. Bonpland and myself inflower and in fruit, there were 654 monocotyledones, and 3226dicotyledones: hence the great division of monocotyledones wouldbe \( \frac{1}{6} \) of the phænogamous plants. According to Mr Brown, theproportion is generally in the Old Continent (in India, Equi-noctial Africa, and New Holland,) \( \frac{1}{5} \). In the temperate zone, we find (according to my Proleg. p. xii.and the partial results published by M. Decandolle, Dict. desSciences Nat. vol. xviii. p. 594,—597.) that the monocotyledonesare to the dicotyledones, |Spaltenumbruch|
  • In Barbary, ‒ ‒ = 1:4,8
  • Egypt. ‒ ‒ = 1:5,0
  • Caucasus and Crimea, = 1:6,0
  • Kingdom of Naples, = 1:4,7
  • The State of Venice, = 1:4,0
|Spaltenumbruch|
  • In France, ‒ ‒ ‒ = 1,4,7
  • Germany, ‒ ‒ = 1:4,0
  • Switzerland, ‒ ‒ = 1:4,3
  • The British Isles, ‒ = 1:3,6
  • North America, ‒ = 1:4,6
In the frigid zone, the proportion is,
  • In Lapland, ‒ ‒ ‒ = 1:2,8
  • Iceland, ‒ ‒ = 1:2,8
We see, that, from the tropics to the pole, the relative increaseof the monocotyledones is very regular. As the monocotyledonesaffect moisture, they are more numerous in the British Isles,and more rare in Egypt and on the dry mountains of Caucasus.I have already observed, that in the Alps of Switzerland, up tothe region of the Rhododendra, the monocotyledones are to the|51| phænogamous plants as 1:7, while in the plains, they are, atthe foot of the Alps, as 1:4,3, (Prolegomena, p. lii.) In the most fertile part of Europe, at the centre of the tem-perate zone, an extent of country of 30,000 square leagues pro-duces about 6000 species of plants, of which 2200 are acotyle-donous or cryptogamous, and 3800 phænogamous. Amongthe last there are nearly 500 Compositæ, 300 Gramineæ, (ex-clusive of the Cyperaceæ and Junceæ), 250 Leguminosæ, and200 Cruciferæ; but only 70 Amentaceæ, 50 Euphorbiaceæ, and25 Malvaceæ. The great families constitute from \( \frac{1}{7} \) to \( \frac{1}{20} \), thesmall ones about \( \frac{1}{50} \) of the total mass of phænogamous plants.This is, so to speak, the mean state of the vegetation in Europe,in the fertile countries, between 42° and 50° of N. Lat. Toconvince the most incredulous of the reality of fixed proportions,or of the regularity to be observed in Europe in the distribu-tion of forms in a particular zone, I shall here present the pro-portions given by two neighbouring countries, France and Ger-many. The figures marked in the following Table may beregarded as the coefficients of each family; for, on multiplyingthe number of phænogamous plants of the temperate zone ofEurope by 0.076 or 0.053, the number of species which composethe families of Gramineæ or Cruciferæ may be found. |Spaltenumbruch|
  • Compositæ,
    • Fr. \( \frac{1}{7.4}=0.135 \)
    • Ger. \( \frac{1}{8}=0.125 \)
  • Glumaceæ,
    • Fr. \( \frac{1}{7.9}=0.127 \)
    • Ger. \( \frac{1}{7.1}=0.141 \)
  • Gramineæalone,
    • Fr. \( \frac{1}{13}=0.077 \)
    • Ger. \( \frac{1}{13}=0.077 \)
  • Legumi-nosæ,
    • Fr. \( \frac{1}{16}=0.063 \)
    • Ger. \( \frac{1}{18}=0.056 \)
  • Cruciferæ,
    • Fr. \( \frac{1}{19}=0.052 \)
    • Ger. \( \frac{1}{18}=0.056 \)
  • Umbelli-feræ,
    • Fr. \( \frac{1}{21}=0.048 \)
    • Ger. \( \frac{1}{22}=0.046 \)
  • Labiatæ,
    • Fr. \( \frac{1}{24}=0.042 \)
    • Ger. \( \frac{1}{26}=0.038 \)
  • Cyperaceæalone,
    • Fr. \( \frac{1}{27}=0.037 \)
    • Ger. \( \frac{1}{18}=0.056 \)
  • Amenta-ceæ,
    • Fr. \( \frac{1}{50}=0.020 \)
    • Ger. \( \frac{1}{40}=0.025 \)
  • Orchideæ,
    • Fr. \( \frac{1}{67}=0.015 \)
    • Ger. \( \frac{1}{43}=0.023 \)
  • Boragines,
    • Fr. \( \frac{1}{74}=0.014 \)
    • Ger. \( \frac{1}{72}=0.014 \)
  • Rubiaceæ.
    • Fr. \( \frac{1}{75}=0.014 \)
    • Ger. \( \frac{1}{70}=0.014 \)
  • Euphorbia-ceæ,
    • Fr. \( \frac{1}{70}=0.014 \)
    • Ger. \( \frac{1}{100}=0.010 \)
  • Junceæ,
    • Fr. \( \frac{1}{85}=0.012 \)
    • Ger. \( \frac{1}{94}=0.011 \)
  • Ericeæ,
    • Fr. \( \frac{1}{125}=0.008 \)
    • Ger. \( \frac{1}{90}=0.011 \)
  • Malvaceæ,
    • Fr. \( \frac{1}{140}=0.007 \)
    • Ger. \( \frac{1}{250}=0.004 \)
  • Coniferæ,
    • Fr. \( \frac{1}{192}=0.005 \)
    • Ger. \( \frac{1}{269}=0.004 \)
|52| This agreement in the greater part of the results is the morestriking, that the coefficients have been obtained from very un-equal masses of plants. In France 3645, in Germany only1844 phænogamous plants have been employed, in order to de-termine the particular proportions of the families. Since thetwo countries border on each other, the species should in likemanner be much the same. The agreement of the results with-in limits thus marked (the greater part commonly within \( \frac{1}{8} \) ofdifference), prove two facts equally remarkable: 1st, That the1700 to 1800 species of phænogamous plants which the Frenchcatalogue has more than the excellent catalogue of M. Schraderemployed for Germany, are distributed among the different fa-milies almost in the same proportions which we observe amongthe plants common to the two countries: 2d, That the speciesof Leguminosæ, of Cruciferæ, and of Umbelliferæ, which Ger-many would appear to possess exclusively, are substituted inFrance by a nearly equal number of species belonging to thesame families. In general, where the greatest discrepancies areobserved, they may be attributed to the circumstance, that Ger-many is situate more to the north than France is. We knowthat the Cyperaceæ and the Ericeæ increase so rapidly towardsthe north pole, that, while in the temperate zone the Cyperaceæare \( \frac{1}{20} \), and the Ericeæ \( \frac{1}{100} \), in the frigid zone there is \( \frac{1}{9} \) of Cy-peraceæ, and \( \frac{1}{25} \) of Ericeæ. On the other hand, the propor-tions of the Orchideæ, of the Malvaceæ, and of the Euphor-biaceæ, increase with equal rapidity towards the south. On com-paring the preceding table with the table of the three zones,(the torrid, the temperate, and frigid), we observe the samelaws. I have added to this comparative table of the vegeta-tion of France and Germany the arrows which, in the generaltable, indicate the directions of increase, from the pole to theequator, and from the equator to the pole. It is a very re-markable circumstance, also, that the coefficients of the fa-milies do not change so much, if, instead of examining exten-sive countries which have from 2600 to 3800 species of phæno-gamous plants, we confine our researches to an extent of somesquare leagues; for example, to the Flora of Berlin, which,according to the work of M. Kunth, comprehends only 900 spe-cies. In that small extent of land, the Leguminosæ are \( \frac{1}{19} \),|53| (in the whole of France \( \frac{1}{16} \), in the whole of Germany \( \frac{1}{18} \)); theGlumaceæ \( \frac{1}{6} \), (in France \( \frac{1}{7.9} \), in Germany \( \frac{1}{7} \),) of the whole massof phænogamous plants. In the same way that the system of climates of the New Con-tinent differs essentially from that of the Old, on account of theunequal distribution of the heat among the different parts of theyear, so also the system of agroupment of American plants hasits peculiar features. It is to the new researches of botanicalarithmetic that we owe the knowledge of these contrasts betweenthe temperate zones of the two worlds. I have thrown togetherin the following Table the results of the American Flora ofPursh and of the French Flora of M. Decandolle. I haveadded certain coefficients of the European frigid region, in or-der to show how much of a boreal character the American tem-perate region presents in the five families of Ericeæ (and Rho-dodendra), Coniferæ, Amentaceæ, Umbelliferæ, and Labiatæ. |Spaltenumbruch|
Temp.America. France. Lapland.
Compositæ, \( \frac{1}{6} \) \( \frac{1}{7} \) 0
Glumaceæ, \( \frac{1}{8} \) \( \frac{1}{7.9} \) 0
Gramineæ alone, \( \frac{1}{10} \) \( \frac{1}{15} \) 0
Junceæ alone, \( \frac{1}{125} \) \( \frac{1}{85} \) 0
Cyperaceæ alone, \( \frac{1}{40} \) \( \frac{1}{27} \) 0
Cruciferæ, \( \frac{1}{62} \) \( \frac{1}{19} \) 0
Leguminosæ, \( \frac{1}{19} \) \( \frac{1}{16} \) 0
|Spaltenumbruch|
Temp.America. France. Lapland.
Malvaceæ, \( \frac{1}{125} \) \( \frac{1}{140} \) 0
Labiatæ, \( \frac{1}{40} \) \( \frac{1}{24} \) \( \frac{1}{70} \)
Ericeæ andRhododendra,} \( \frac{1}{36} \) \( \frac{1}{125} \) \( \frac{1}{25} \)
Umbelliferæ, \( \frac{1}{57} \) \( \frac{1}{20} \) \( \frac{1}{25} \)
Amentaceæ, \( \frac{1}{25} \) \( \frac{1}{50} \) \( \frac{1}{51} \)
Coniferæ, \( \frac{1}{103} \) \( \frac{1}{200} \) \( \frac{1}{160} \)
The differences which are manifested in this table betweenthe two continents, bear, not merely upon the five last families,which might be called boreal forms, but also upon the Cruciferæ,the Junceæ, and the Cyperaceæ, which are equally rare in thetorrid zone and in the temperate zone of the New Continent. It is conceived that the inquiries regarding the numericalproportions of vegetable families, will present results much moreinteresting when the Floras of different countries shall be cir-cumscribed within more precise geographical limits, and whenbotanists shall attend more particularly to the principles accord-ing to which varieties and species ought to be distinguished.The catalogues which we see under the vague name of Flora ofthe United States of America, comprehend countries placedin very different climates, from 18° to 9° of mean temperature.Here we have a difference of climate as great as in Europe be-|54| tween Calabria and Austria. When the vegetation of SouthCarolina, of Pennsylvania, and of New England, shall be de-scribed individually, and with the same degree of exactness, weshall notice a regular increase and decrease in the numerical pro-portions of families from south to north. At present, we onlyknow the general mean of these partial proportions. Manycountries seem richer in plants, because the botanists have in-considerately elevated varieties to the rank of species. In an-other country, the travellers often neglect the plants which theybelieve to be the same as those of their own country. But whenwe attend to the great divisions, and when the number of spe-cies which we compare is very considerable, our researches arefavoured with happy compensations. It is thus that the newFloras, much more complete of America and Lapland, publishedby Messrs Pursh and Wahlenberg, have not sensibly alteredthe numerical proportions which we find on confining ourselvesto the old Floras of Michaux and Linnæus, (Berl. Jahrb. der Gew. b. i. s. 24.). Whatever may be the corrections which shallbe made in my work, I am persuaded beforehand, that the morethat exact observations are accumulated, and the more we lookbeyond the same hemisphere, the same system of agroupment, thepartial variations of the coefficients will be found not to be madeby sudden starts, but according to invariable laws. It may bethat the tropical proportion of the Malvaceæ is \( \frac{1}{32} \) or \( \frac{1}{33} \), in-stead of \( \frac{1}{35} \), but it is not the less certain, that the Leguminosæand the Malvaceæ increase toward the equator, while the Jun-ceæ and the Ericeæ increase toward the pole. One may recallin doubt the quantities of the variations, the rapidity of the in-crease, but not its direction. On comparing the coefficients which belong to the same fa-milies, in different zones, we find, in the rapidity of the increase,contrasts strongly marked. In the Old Continent, the propor-tions of the Gramineæ, the Leguminosæ, and the Euphorbia-ceæ, change much less from the temperate zone to the equator,than from the temperate zone to the pole. Those who are accustomed to consider each phenomenon inan absolute and irrelative point of view,—who regard the meantemperature of places, the laws which are observed in the varia-tions of terrestrial magnetism, with the proportions between births|55| and deaths, as daring hypotheses, and as vague, theoretical spe-culations,—will probably look with contempt on the discussionswhich form the principal object of this memoir. Those, on theother hand, who delight to contemplate the mutual concatenationof organized beings,—who are aware that the numerical resultscorrect themselves by the accumulation and the careful investi-gation of particular facts,—will cherish a kind of research,which throws light upon the economy of Nature,—on the con-nection which is observed between the climates and the form ofbeings,—on the distribution of plants and of animals in thedifferent regions of our planet. It is only by the numericalexamination and the comparison of species, that we can form acorrect idea of the state of the vegetation of a given country;—of the general influence which the temperature exercises overthe frequency of certain forms, near the equator, in the meanparallel, and towards the polar circle;—of the characteristic fea-tures which distinguish, in isothermal zones, the two systems ofagroupment of the Old and the New World *.

* For the use of such as have not made descriptive botany their particularstudy, and who are yet desirous of acquiring a knowledge of the investigations whichhave been attempted in the different branches of the natural sciences, we shall addin this place the names of some of the most common plants which characterise, ifwe may so speak, the tribes or families which are frequently the subject of discus-sion in this memoir. (The translation of the following is modified so as to givean English reader an idea of the families). Junceæ (Rushes); Cyperaceæ (Hard orMoor Grasses, Cotton-Grass); Gramineæ (Corn, Grasses); Compositæ (Dandelion,Thistles, Sunflower); Leguminosæ or Papilionaceæ (Vetches, Pease, Clover); Ru-biaceæ (Rennet, Madder); Euphorbiaceæ (Sun-spurge, Dogs’ Mercury); Labiatæ(Mint, Thyme, Rosemary); Malvaceæ (Mallows, Hollyhock); Umbelliferæ (Carrot,Hemlock, Chervil, Carraway); Cruciferæ (Mustard, Cresses, Radish, Turnip).The great mass of plants which cover the globe is divided by botanists intoPhænogamous (those having visible flowers), and Cryptogamous or Agamous (Ferns,Lichens, Mushrooms).