268 BOTANICAL GAZETTE [OCTOBER 
(fig. 35) connected with a longitudinal half of a node was submersed 
in water and formed adventitious roots in nine days. The leaf 
(fig. 36) attached to a whole node formed no adventitious roots 
under the same conditions. 
IX. Isolation, inhibition, and the flow of material 
through the plant 
These rules give us some basis on which we may try to form a 
preliminary idea on the nature of the mechanism of inhibition. 
As we mentioned already, the rules are com- 
prehensible if we assume a flow of certain 
, (possibly specific) substances (or formed cells) 
from the places where the dormant buds are 
ready to grow, or the prevention of such a 
flow toward these dormant buds. 
We will first show in a few simple 
examples that this idea leads us easily 
through the maze of facts in which the terms 
isolation or inhibition have no more than a 
metaphorical value. 
When we isolate a leaf and suspend it in 
moist air or put it into a Petri dish the bottom 
of which is covered with water, as a rule 
) only a few of the notches will grow out into 
shoots. Why do not all grow out? From 
what was said in the previous section it was 
ee natural to expect that the growth of the 
shoots in some of the notches of a leaf inhibits 
the growth in the rest of the notches of the 
same leaf, and that if all the notches could be isolated from each 
other this inhibiting effect would cease and they would all grow out. 
This idea was put to a test in a way indicated in fig. 37. Five 
notches on one side of a leaf were isolated from the leaf and from 
each other. The rest of the leaf and the isolated notches were 
put into a Petri dish whose bottom was covered with a layer of 
water. All five isolated notches grew out into shoots, while only 
three of the ten or twelve notches left on the leaf grew out. This 
Fics. 30-32 
