292 Schively — Contributions to the Life History of 



twining, although the shoots varied in length from twelve 

 to eighteen inches. The main stem had grown but little. 



When plants much older than these (about three feet 

 high) were similarly treated, no results were obtained. 

 The shoots remained white and did not seem to increase in 

 length, and finally died. 



Another experiment was as follows: A vigorous plant 

 was truncated just above the simple leaves; every axillary 

 bud was removed, and this process was repeated, no bud 

 being allowed to develop. The result was that in the 

 course of about ten days two cotyledon ary shoots had arisen 

 from the soil. Later on twining took place. 



Referring for a few moments to the paragraphs upon the 

 development of cotyledonary buds, (p. 284) it will be found 

 that when the main stem is destroyed, and the developing 

 shoots take its place, twining becomes their habit. Yet if 

 the stem persists, and they are brought above ground, their 

 growth is more or less horizontal. 



Thus the cotyledonary shoots, and the axillary runners, 

 which under normal natural conditions are geotropic, may 

 acquire apogeotropic tendencies, if necessity places certain 

 responsibilities upon them. 



Illustrations need not be multiplied; enough has been 

 said to indicate the deep resources of the plant. In the 

 "struggle for existence " many, if not all, of the conditions 

 artificially produced, no doubt do occur. Very beautifully 

 does Ampliicarpcea show its ability to cope with adverse cir- 

 cumstances, and by various growth-compensations to pro- 

 long its existence, and even to continue its accustomed 

 habits of twining. 



ClRCUMNUTATlON EXPERIMENTS. 

 In his writings, Darwin includes under the term circum- 

 nutation, the movements of heliotropic organs, those of geo- 

 tropic organs, as well as those of the twining stem. Under 

 the last heading, belong the principal experiments to be 

 described in this section. 



