10 INTRODUCTION 



lar appearance, although the actual species are rarely the 

 same or even closely related. For example, there are no 

 cacti in the Sahara Desert but there are plants closely 

 resembling them which are not nearly related. On the 

 other hand, related species are usually found in the same 

 general region although they may not resemble one an- 

 other in appearance or live in similar habitats. This 

 study of the adaptation of organisms to their surround- 

 ings has a practical side also, in that successful agricul- 

 ture consists very largely in providing the most suitable 

 environment for each particular crop. Thus, the U. S. 

 Department of Agriculture experts are often able to pre- 

 dict what sort of crops will do well under cultivation 

 on wild lands by observing the plants growing on them 

 in nature. This is, of course, only a beginning, for the 

 chief object of the scientific agriculturist is to devise 

 still more favorable conditions of growth for his animals 

 and plants. 



12. Man's Place in Nature is certainly one of the 

 subjects of greatest importance and interest to himself. 

 It is, therefore, well to understand in what ways he is 

 subject to the same limitations as other animals, and in 

 what ways he differs from them and is their superior in 

 molding and transforming his environment to suit his 

 needs or convenience. It may be disappointing to find 

 that he has far more in common with them than other- 

 wise. However, the differences, small as tlicy are, make 

 him largely the master of the destiny of his race and an 

 important influence on all nature. 



