194 ILLINOIS STATE ACADEMY OF SCIENCE 



notch growth in each of the 5 isolated leaves. 4 leaves 

 with stems had both axillary shoots; the fifth had just 

 the opposite shoot. These leaves are shown in Plate 

 VII. The notch growth on the leaves having a portion of 

 the stem attached was as abundant in the 4 specimens 

 having both axillary shoots as it was in the isolated 

 leaves. The axillary shoot had lost its inhibiting effect. 



When leaf 1 of B. crenatum was suspended in moist 

 air and deprived of light, the buds developed in most of 

 the notches within 7 days. In 5 weeks the shoots were 

 fully an inch long. 



The purpose of these experiments was not to discover 

 the cause of regeneration, but rather to determine 

 whether the rules given by Loeb for B. calycinum could 

 be applied to B. crenatum. 



Loeb assumed that the cause of regeneration was the 

 prevention of the flow of material from the notches of 

 the leaf, and he was supported in this view by his experi- 

 ments on B. calycinum. No such simple explanation can 

 be given for B. crenatum. If a piece of stem was left 

 attached to the leaf, leaf 2, one or both axillary buds de- 

 veloped. A comparison of this leaf with the isolated 

 node from near the apex of the plant shows the growth 

 of the buds about the same in leaf 2, altho in the latter 

 case there were no leaves from which the buds could get 

 this flow of material. 



In a later experiment, 2 Loeb finds that an apical leaf 

 influences the lower buds of its side of the stem. He 

 states, in this connection, that the inhibiting influence of 

 the leaf upon shoot formation is due to an inhibiting sub- 

 stance which is secreted by the leaf and carried with the 

 sap toward the lower part of the stem. No such sub- 

 stance seems to be produced in B. crenatum. 



Although the development of the axillary buds and 

 notch growth is hastened by the separation of leaf or 

 stem from the plant, Goebel 3 found in his experiments 

 with B. crenatum that the development of the notch 

 growth on leaves attached to the plant could be brought 

 about by cutting squarely across the middle vein near 

 the base of the leaf. If a longitudinal cut was made near 

 the edge of the leaf no growth occurred. He attributed 



