ORIGINAL BIOTA OF THE AMERICAS 



tables have been developed to show the 

 relations of the two kinds of regions. 



I. NORTH AMERICA NORTH OP MEXICO 



The accompanying maps (figs. 1, 2, 

 and 3) show the more important exten- 

 sive habitats drawn so far as practicable 

 on the basis of dominant landscape 

 aspect conditions. In differentiating 

 the areas, plants, animals, and climate 

 were considered. 



a. Plants and animals 



From the standpoint of the larger 

 animals the following are of much im- 

 portance and should tend to outweigh 

 minor botanical considerations: 



Is the forest evergreen or do the 

 leaves fall, thus accentuating the sever- 

 ity of adverse seasons? 



Are grasses or other plants present 

 which afford dry food in cold or dry 

 seasons? 



Is the vegetation of such height and 

 density as to afford shelter for larger 

 animals, or is it short-stemmed and 



inconspicuous, or scattered and non- 

 shade producing? 



b. Climate 



The most important question about 

 climate is probably the character of 

 the annual march of rainfall, of tem- 

 perature, and of other factors. 



The accompanying maps 1 are very 

 generalized. Figure 1 is based largely 

 on Shreve's map for the United States, 

 on the maps of Schimper and of Hardy 

 on Koppen's Classification of climate, 

 and Bartholomew's Atlas. The de- 

 scriptions of vegetation are modifica- 

 tions of Shreve's. Some modifications 

 of the plant regions have been made 

 because of facts about animals. For 

 instance, an area like the Snake River 

 Plains which once supported herds of 

 bison should hardly be called desert. 



1 Submitted to the members of the committee. 

 Suggestions by B. E. Livingston, F. Shreve, W. E. 

 Lawrence, H. C. Cowles, G. B. Rigg, G. E. Nichols, 

 C. D. Howe, E. N. Transeau, J. W. Harshberger, 

 G. P. Burns, C. O. Rosendahl, E. Lucy Braun, R. 

 M. Harper (botanists) and J. R. Watson, W. G. 

 Van Name, A. S. Pearse (zoologists) were adopted 

 and are as represented in figure 3 and those parts 

 of the United States shown in figure 4. 



