152 BOTANICAL GAZETTE [FEBRUARY 
the material required for their growth, for if we cut out short 
pieces with one node only (fig. 4, a, 6, c, d), the growth of the shoots 
from the buds is retarded. This is not the only factor of inhibition 
in this case, since the writer has recently shown® that 
a growing bud, as well as a leaf, seems to send out 
inhibitory substances toward the base of the stem which 
prevent the buds in the stem, situated more basally, 
from growing out. This factor of inhibition will not be con- 
sidered in this paper. 
We shall try to show in this paper that the quantity of 
material available for the formation of shoots is definite and 
limited, and that inhibition may result from the retention or 
utilization of part of this material by the inhibiting organ. 
A preliminary note of these results has already been pub- 
lished.7 
Each notch of a leaf of Bryophyllum calycinum can give 
rise to a shoot when the leaf is cut off from the stem and 
suspended in moist air, but as a rule only a few of these 
notches will grow into new plants. When we cut the leaf 
into as many pieces as there are notches, practically each 
piece (very small ones only excepted) will give rise to a 
shoot. Figs. 5 and 6 are sister leaves. Leaf 5 is cut into as 
many pieces as there are notches, while leaf 6 is left intact. 
Both were kept on moist filter 
paper. Leaf 5 has given rise to a 
new shoot in 
practically each 
notch, while 
leaf 6 has formed 
only 4 shoots. 
We assume that 
in the latter leaf 
the shoots which ) | b c ad 
Ce 
- 
YU 
“ 
é 
Fic. 4.—Shows that inhibited —_ cage - st long stem accelerates growth of 
the two apical buds, since in pieces wit y (a, 6, c, d) the buds do not grow 
at all, or much more slow 
6 Logs, J., Science 46:547. 1917. 7 [bid., 45:436. 1917. 
