358 Schively — Contributions to the Life History of 



9. Axillary runners from the simple leaves [i. <?., first pair 

 of green leaves) in their natural condition are geotropic and 

 refuse to twine. When, however, the main stem is de- 

 stroyed, these runners become apogeotropic and twine well. 



10. Axillary shoots from compound leaves soon exhibit 

 apogeotropic tendencies, and twine. If the main stem of 

 the plant is destroyed, axillary shoots from any compound 

 leaf will readily continue the twining habit of growth. 



ii. Circumnutation experiments show for Amphicarpcea 

 the most rapid rate of movement known for a twining 

 plant. A complete revolution may be made in 5 1 minutes. 

 The optimum temperature is from 26 C. to 3 2° C. ; the 

 behavior is greatly modified by environmental conditions. 



12. In early development numerous crystals appear in 

 the cells forming the inner row of the cortex of the stem. 

 These ultimately constitute a distinct crystal sheath. 

 The crystals are somewhat prismatic in form, possessing 

 an apparent partition across the middle. These twin 

 structures occur also round the vascular areas of the leaves, 

 and also in the cortex of the pulvini. 



13. All green leaves are capable of assuming normal, 

 paraheliotropic and nyctitropic positions. These positions 

 are absolutely dissimilar. 



14. When young, the simple leaves assume peculiar 

 paraheliotropic and nyctitropic positions. 



15. All leaflets manifest great activity during the night 

 hours. 



16. Amphicarpcea produces four types of flower: (a) 

 purple aerial, (b) green aerial, (c) subterranean, (d) winter 

 aerial. A comparison of these leads to the conclusion that the 

 purple aerial is the original type, and that by a series of 

 transitions through (b) and (d) the most reduced type (c) is 

 reached. These variations are doubtless due to the environ 

 mental conditions under which they are produced. 



17. Purple flowers are not produced during the winter, 

 even though the greenhouse is kept at a high temperature. 

 It is believed that the non-production of these flowers and 



