ON XEROPHYTIC ADAPTATIONS OF LEAF 

 STRUCTURE IN YUCCAS, AGAVES 

 AND NOLINAS 1 

 PROFESSOR J. F. McCLENDON 

 University of Missouri 



Zoology and botany are now so separated, and for a 

 worker in one field to venture into the other is so unusual 

 that it may not be out of place to state my reasons for 

 presenting this paper, which are as follows : 



1. Practically all of the material was worked up in 

 1903-4, and since I shall not have opportunity to complete 

 the study I wish to make this part available. 



2. I wish to emphasize the importance of the results of 

 plant physiology to the zoologist. Many of those phe- 

 nomena now brought into such prominence in zoology 

 (i. e., trophisms, heteromorphosis and the mutually anti- 

 toxic action of sodium and calcium) were discovered in 

 plants and later studied in animals. Likewise the study 

 of the water economy of desert plants may ultimately 

 throw some light on similar processes in animals that are 

 subjected to constant (i. e., Dermestes) or periodic lack 

 of water (i. e., rotifers). The cutin of plants and the 

 chitin of animals play similar roles, and it may be that 

 the carbohydrate and mucoid (?) water-storing sub- 

 stances in plants have analogues in animals. 



I am indebted to Dr. W. L. Bray for suggesting and 

 directing this study, and for procuring the material, most 

 of which he obtained from Langtry, Texas and from the 

 Missouri Botanical Garden. 



Methods.— The most serviceable method for investiga- 

 ting cell walls was free-hand sections stained in chlorio- 



1 Contribution from the Botanical Laboratory of the University of Texas 

 under the direction of Dr. W. L. Bray. 



308 



