1915] LOEB—REGEN ERATION 253 
bud of its stem a shoot will grow (S in figs. 2 and 4); and in the 
leaves 3 tiny roots may begin to grow from the notches which, 
however, usually dry up after some time; and no shoots are formed 
if the leaf is suspended entirely in moist air. 
III. Inhibition of growth of leaves by growth of buds on stem 
The question now arises: Why does the presence of the piece of 
main stem in fig. 2 inhibit or retard the formation of roots and 
shoots in the notches of the leaf, and why does the same piece 
of stem cease to inhibit (or why does it inhibit considerably less) 
when, as in fig. 3, in addition 
to the stem another leaf is 
left with it? Each node has 
two buds, one in the axilla of S 
each leaf. When we use a 
specimen, as fig. 2, a shoot 
(S) will grow out in a few 
days from that bud of the 
stem where the Jeaf is 
removed; and this is the first 
growth which will occur in 
this specimen. The bud in ho 
the axilla of the leaf which is 
preserved will as a rule not 5 
grow out. In fig. 3, where Fics. 4 AND 5 
both leaves are preserved, 
neither bud of the stem wil] grow out in winter.? Hence we 
notice that where a shoot grows out very rapidly from the bud 
of the stem, as in fig. 2, the leaf in contact with the stem is 
prevented or delayed in forming roots and shoots, but when no 
such shoots grow out from the bud of the stem (as in fig. 3), the 
notches of the leaf (if submersed in water) will form roots and 
shoots rather quickly. 
2 In the spring this is not so strictly true, but all these experiments were made in 
a greenhouse during the winter months. The greenhouse had a temperature of 70° F. 
or above. 
