274 BOTANICAL GAZETTE [OCTOBER 
We have assumed that if we have a node with its two leaves 
attached, the flow will be deflected from the buds; this again is in 
harmony with the facts that in such a case as a rule neither of the 
buds grows out. 
When a plant is normal, it is almost or possibly absolutely 
impossible to induce the notches of a leaf which is connected with 
the plant to grow. The writer has submersed such leaves in water, 
but in months not a single notch ever formed a root or a shoot. I, 
however, the flow of substances in a plant is abnormal, either 
because the roots or the apical parts or both have suffered, a 
growth of shoots may occur in moist air from the notches of leaves 
which are in contact with the plant. This fact is mentioned by 
DeVries and is well known to those who have seen the plants in 
their natural conditions in Bermuda. 
If we now return to the question from which we started, namely, 
why it is that the notches of the leaves of Bryophyllum will not 
grow out while in connection with the normal plant, the answer 
should be that the flow of material from the root and from the 
leaves into the stem and to the apical end of the latter prevents this 
growth. Through this flow material is carried away from the 
notches of the leaves. The anatomy of the conducting vessels and 
tissues, which is inherited, and the dynamical factors determining 
the flow are the factors concealed in the term ‘‘correlation.” We 
understand why it is that if we isolate a part, buds may grow out 
which without the isolation would not have grown, the reason being 
that in the mutilated part material can flow to and be retained at 
places where if the part had remained in the whole it could not have 
been retained. This assumption agrees with the older ideas of 
DutTrocHet, SAcHs, DeVries, and GorBEL on regeneration in 
plants. We understand on this basis why it is that the term iso- 
lation of parts or the inhibiting effect of growing parts on others 
may express some but not all the facts of regeneration. It is not 
the isolation in itself, but the retention of material in places where 
there would not have been such a retention under ordinary condi- 
tions which apparently determines the growth of dormant buds in 
an isolated piece; and so it may happen that while this term 
expresses adequately some results, it fails in others. 
