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|Spaltenumbruch|
Alexander Count Humboldt has sub-mitted to the Institute a curious paper, onthe laws observed in the distribution of ve-getable forms over the globe.
The vegetables, says he, which cover thevast surface of the globe, present, when westudy by natural classes or families, strik-ing differences in the distribution of theirforms. On limiting them to the countriesin which the number of the species is ex-actly known, and by dividing this number
|Spaltenumbruch|by that of the glumaceæ, the leguminousplants, the labiated, and the compound, wefind numerical relations which form veryregular series. We see certain forms be-come more common, from the equator to-wards the pole, like the ferns, the gluma-ceæ, the ericineæ, and the rhododendrons.Other forms, on the contrary, increasefrom the poles towards the equator, andmay be considered in our hemisphere assouthern forms; such are the rubiaceæ,the malvaceæ, the euphorbia, the legumi-nous, and the composite, plants. Finally,others attain their maximum even in thetemperate zone, and diminish also towardsthe equator and the poles; such are thelabiated plants, the amentaceæ, the cruci-feræ, and the umbelliferæ. The grassesform in England 1-12th, in France 1-13th,in North America 1-10th, of all the pha-nerogamous plants. The glumaceæ formin Germany 1-7th, in France 1-8th, inNorth America 1-8th, in New Holland,according to the researches of Mr Brown,1-8th, of the known phanerogamous plants.The composite plants increase a little inthe northern part of the new continent;for, according to the new Flora of Pursch,there is between the parallels of Georgiaand Boston 1-6th, whereas in Germanywe find 1-8th, and in France 1-7th, of thetotal number of the species, with visiblefructification. In the whole temperatezone, the glumaceæ and the compositeplants form together nearly one-fourth ofthe phanerogamous plants; the glumaceæ,the compositæ, the cruciferæ, and the le-guminosæ, together, nearly one-third. Itresults from these researches, that the formsof organized beings are in a mutual depen-dence; and that the unity of nature issuch, that the forms are limited, the oneafter the other, according to constant lawseasy of determination.
The number of vegetable species de-scribed by botanists, or existing in Euro-pean herbals, extends to 44,000, of which6000 are agamous. In this number wehad already included 3000 new phaneroga-mous species enumerated by M. Bonplandand myself. France, according to M. De-candolle, possesses 3645 phanerogamousplants, of which 460 are glumaceæ, 490 com-posite, and 230 leguminous, &c. In Lap-land there are only 497 phanerogamousplants; among which are 124 glumaceæ,58 composite, 14 leguminous, 23 amen-taceous, &c.