1890.] The Distribution of Pants. 819 
THE DISTRIBUTION OF PLANTS. 
BY V. M. SPALDING. 
N unusual degree of interest has recently been manifested, 
both in the general subject of the geographical distribution 
of plants, and in the special study of areas occupied by natural 
groups, with reference to questions of relationship. In view of 
this interest, indicated in part by various important papers and 
monographs that have lately appeared, it may be that an outline 
of the historical development of the subject, and the present 
condition of our knowledge in regard to it, may serve a timely 
purpose. 
The history of the philosophical study of geographical distri- 
bution properly begins, with the opening of the present century, 
with the classical essay of Alexander von Humboldt on the 
“ Geography of Plants.”! Fifty years before that time Linnaeus? 
had discussed the habitats of plants, with reference to the physi- 
cal conditions by which they appeared to be determined, and 
somewhat later had considered the dissemination of seeds by 
winds and other agencies, and the influence of climate and lati- 
tude; but Humboldt was the first to approach this study with 
the distinctively scientific spirit that subordinates facts to princi- 
ples, and endeavors to give to all observed phenomena a rational 
explanation. 
Humboldt’s habits of study led him to think of the vegeta- 
tion of the earth from the standpoint of the physical geographer 
rather than that of the biologist. In the “ Ansichten der Natur,” 
published in its final form many years later, the prominence still 
given to physical conditions, and the fixed habit of deriving 
conclusions from numerical data, furnish a striking comment 
! Essai sur la Géographie des Plantes, 1805. 
? For a brief and discriminating reference to the writings of Linnzeus ar the sub- 
ject, and the still earlier observations of Tournefort, see the address of Sir J. D 
. Hooker before the hical Section of the British Association at the York iid 
ing, 1881, where other important references may also be found. 
