CURVATURE OF BRYOPHYLLUM CALYCINUM. 339 



In every case provided the atmosphere was kept saturated, roots 

 appeared with apparently equal facility at any notch. 



G. Regeneration. According to Loeb, the growth of roots and 

 shoots', at the marginal notches of a leaf is ordinarily inhibited, by 

 suction of the stem and especially of the growing axillary buds. To 

 verify this : — 



(1) A piece of the stem of Bryophyllum had one leaf at the basal 

 portion alone left, and it was left in a moist chamber supported in 

 the horizontal position on a board. On the 7th day (Plate I, fig. 11) 

 roots had grown out from the notches of the single leaf, and the 

 opposite bud showed signs of growth. On the 14th day, the bud 

 opposite the basal leaf had fully grown out and several shoots also 

 had appeared from the notches of the basal leaf. Roots had also 

 appeared from the under-side of the basal node. 



Now, if really the opposite bud inhibited the growth in the 

 notches of the basal leaf, one would expect that as the opposite bud 

 began to grow, the roots that had grown from the notches of the 

 basal leaf would not have developed any further. On the contrary, 

 they continued to grow, and shoots also appeared from the notches. 

 In short, the growth in the notches of the leaf, progressed side by side 

 with the growth of the opposite bud. Hence, apparently no inhibi- 

 tion had taken place. 



(2) Two pieces of the stem of Bryophyllum, containing each a 

 single node with only one leaf attached were suspended so that part 

 of the lower leaf was sub-merged in water. After 10 days, it was 

 found that the submerged notches of the lower leaf, in each case, had 

 developed roots, while the opposite bud also was developing. (Plate 

 I, figs. 12 and 13). 



(3) A piece of the stem of Bryophyllum containing a single node 

 with two leaves attached was arranged so that one of the leaves 

 had a part submerged in water. On the 6th day roots were found to 

 have grown out from the notches of the submerged lower leaf. On 

 the 9th day the bud in the axil of the submerged leaf, as well as the 

 bud in the axil of the opposite leaf had developed. The upper leaf 

 withered and finally fell off, and is therefore not seen in the photo- 

 graph (Plate I, fig. 18). A root had also grown from the piece of 

 stem. 



In this case again, if Loeb's inhibition theory were correct, one 

 would expect that since each of the axillary buds inhibited the 

 development of the opposite leaf, none of the two leaves should have 

 grown any roots in their notches. As a matter of fact, the lower 

 submerged leaf produced roots in its notches and its opposite bud 

 also developed, as also the other axillary bud. 



