296 BOTANICAL GAZETTE [OCTOBER 
growing region of the tips of the stem and the roots causes a flow 
of substances away from the leaf. 
In the previous paper the following experiment was described. 
Three leaves were submersed with their tips in water. One leaf 
was completely isolated (fig. 3), the second leaf had a piece of a 
stem attached (fig. 4), and 
the third piece had the 
opposite leaf attached in 
addition to a piece of stem 
(fig. 5). The drawing was 
made 25 days later. The 
completely isolated leaf 
(fig. 3) had formed two long shoots, the leaf in 
fig. 4 had only the two tiny roots, and the sub- 
mersed leaf in fig. 5 had two short shoots. 
The experiment finds its explanation on the 
basis of the observation represented in figs. 1 
and 2. In fig. 4 the bud of the stem opposite 
the leaf grew out before even the notches in the 
completely isolated leaf of fig. 3 could grow. 
This growth of the bud on the stem acted as a 
center of “suction” on the leaf and created a 
flow away from the notches toward the stem. 
Even when the growth of this bud is prevented 
the stem has a suction effect. In fig. 5, where 
two leaves were left, no shoot would grow out 
Fic. 7 from the stem, and hence shoots could grow 
out from the immersed leaf, but not as rapidly 
as in the completely isolated leaf (fig. 3), showing that probably, 
using the symbol of a “‘suction,” some suction must have been 
caused by the stem, but not as much as if the opposite leaf had not 
existed. 
The writer was anxious to see whether this experiment would 
not succeed when the whole leaves are suspended in moist air 
instead of submersing the tips in water. This latter form of the 
experiment has the drawback that in the leaf with a stem (fig. 4) the 
growth of the notches in the submersed part is often not entirely 
