REPORT OF THE PRESIDENT, 191G. 9 



the precision now attained in such determinations is incom- 

 parably superior to that attainable by the pioneers in this science 

 twenty centuries ago. 



Whatever may be our prepossessions or our reasoned convic- 

 tions, those who have read Darwin's Origin of Species, or so much 

 as the last paragraph thereof, must agree with him that "It is 

 interesting to contemplate a tangled bank, clothed with many 

 plants of many kinds, with birds singing on the bushes, with 

 various insects flitting about, and with worms crawling through 

 the dam^p earth, and to reflect that these elaborately constructed 

 forms, so different from each other, and so dependent on each 

 other in so complex a manner, have all been produced by laws 

 acting around us." Even the um-eflective farmer has noticed 

 such tangled banks and has learned that noxious weeds will 

 invade his fields and vanquish his crops if he is not dul}^ vigilant. 

 A considerable knowledge of biology, of plant, insect, and animal 

 hfe is, indeed, now essential to successful economic husbandry; 

 but although tradition has furnished a large aggregate of useful 

 inductions for the needs of agriculture and horticulture, it is only 

 in recent decades, dating substantial^ from the advent (1859) of 

 Darwin's great work, that such inductions have begun to rise 

 to the level of coordinated knowledge. It is in line with this 

 general advance in biological science that the Department of 

 Botanical Research finds reasons for its existence; and its activ- 

 ities accordingly have been devoted chiefly to investigations of 

 the conditions of existence, the migrations, the mutations, etc., of 

 species, families, and groups of plants, especially those character- 

 istic of deserts. Naturally, this large domain for research has 

 led to much division of labor and to much collaboration with 

 many experts possessing special acquaintance severally with the 

 numerous problems presented. During the past four years Dr. 

 Frederic E. Clements, professor of botany in the University of 

 ^Minnesota, has been attached to the Department as a Research 

 Associate and has extended the field studies and elaborated the 

 inductions on which he had been at work previously for many 

 years. The results of his investigations are embodied in a 

 remarkable book entitled "Plant Succession: An Analysis of the 

 Development of Vegetation." This work extends the concepts 

 of Darwin so vividly called to mind by the "tangled bank" 



