Botany and Zoology. 167 



statistics and comparisons which have not before been attempted 

 owing to scarcity of material. Although it is impossible to give 

 within the narrow limits of this review even a partial idea of the 

 facts upon which Mr. Hemsley's conclusions are based, the en- 

 deavor will be made in a future notice to indicate his method of 

 exposition and to state the general results which he has reached. 

 The present short mention can only give a few citations from Sir 

 Joseph Hooker's " Commentary " above referred to, in order to 

 outline two views relative to the primary divisions of the vegeta- 

 tion of the globe. In contrasting the two views, it may be well 

 to keep in mind the practical division made by Mr. Thiselton 

 Dyer, namely, into "Northern, Tropical, and Southern." 



Mr. Hemsley's Introduction, with which the Commentary 

 deals, comprises about 50 pages. It is devoted mainly to the 

 presentation of general statistics regarding phanerogamous vege- 

 tation, its division into regions, and, especially, a contrast of the 

 flowering plants of Mexico (including those of Central America) 

 with those of India. The approaching completion of Hooker's 

 "Flora of British India" renders this contrast for the first time 

 possible. The areas contrasted are within nearly the same 

 parallels of latitude, namely, 9° N. and 35° N. but they are sepa- 

 rated by about 180° of longitude, the American 80° to 115° W., 

 the Asiatic 10° E. to 95° E. 



Of these widely separated regions, Sir Joseph Hooker says in 

 his interesting commentary on Mr. Hemsley's work, "Each pre- 

 sents a hot and moist tropical, a temperate, and a frigid climate. It 

 is impossible to find in the Old and New Worlds respectively, two 

 areas more similar as to physical features, or in which the vegeta- 

 tion of their respective continents is more fully represented; and 

 yet the comparison of their floras shows that with an almost 

 total diversity of species genera and of many natural orders, the 

 proportion of monocotyledonous to dicotyledonous plants is 

 nearly the same in each ; that the number of natural orders is 

 only 12 fewer in Mexico; that the number of species in each 

 differs by only 2000 (11,626 in Mexico, 13,647 in India) ; that the 

 average number of genera in each order is neaiiy the same* in 

 each (11 in Mexico and 13 in India) that the average number of 

 species in each genus even more nearly coincides (6*4 in Mexico 

 and 6 - in India), and more singular still, that the percentage of 

 endemic species in each differs by only 2 per cent. It is instruc- 

 tive to observe that these marked resemblances in proportions do 

 not arise out of a resemblance in the elements from which they 

 are derived ; for, turning to the natural orders that contribute most 

 largely to the Flora of each area, they are very differently repre- 

 sented as to the number of species in each. Compositae, which 

 take the first place in the Flora of the globe and of Mexico, are 

 reduced to the sixth place in India. Leguminosse, which are sec- 

 ond to Compositae alone, are second in both Mexico and India, 

 but Orchidacese, which hold the third place in the world and in 

 Mexico, are first in India; Rubiacese, the fourth in the world are 



