Alexander Count Humboldt has submitted to the Institute a curious paper, on the laws observed in the distribution of vegetable forms over the globe.

The vegetables, says he, which cover the vast surface of the globe, present, when we study by natural classes or families, striking differences in the distribution of their forms.

On limiting them to the countries in which the number of the species is exactly known, and by dividing this number by that of the glumaceae, the leguminous plants, the labiated, and the compound, we find numerical relations which form very regular series.

We see certain forms become more common, from the equator towards the pole, like the ferns, the glumaceae, the ericineae, and the rhododendrons.

Other forms, on the contrary, increase from the poles towards the equator, and may be considered in our hemisphere as southern forms; such are the rubiaceae, the malvaceae, the euphorbia, the leguminous, and the composite, plants.

Finally, others attain their maximum even in the temperate zone, and diminish also towards the equator and the poles; such are the labiated plants, the amentaceae, the cruciferae, and the umbelliferae.

The grasses form in England 1-12th, in France 1-13th, in North America 1-10th, of all the phanerogamous plants.

The glumaceae form in Germany 1-7th, in France 1-8th, in North 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 in the northern part of the new continent; for, according to the new Flora of Pursch, there is between the parallels of Georgia and Boston 1-6th, whereas in Germany we find 1-8th, and in France 1-7th, of the total number of the species, with visible fructification.

In the whole temperate zone, the glumaceae and the composite plants form together nearly one-fourth of the phanerogamous plants; the glumaceae, the compositae, the cruciferae, and the leguminosae, together, nearly one-third.

It results from these researches, that the forms of organized beings are in a mutual dependence; and that the unity of nature is such, that the forms are limited, the one after the other, according to constant laws easy of determination.

The number of vegetable species described by botanists, or existing in European herbals, extends to 44,000, of which 6000 are agamous.

In this number we had already included 3000 new phanerogamous species enumerated by M.

Bonpland and myself.

France, according to M. Decandolle, possesses 3645 phanerogamous plants, of which 460 are glumaceae, 490 composite, and 230 leguminous, &c.

In Lapland there are only 497 phanerogamous plants; among which are 124 glumaceae, 58 composite, 14 leguminous, 23 amentaceous, &c.