1915] LOEB—REGEN ERATION 251 
plainly impossible, therefore, to connect in any way the growth of , 
the notches of a leaf with the ‘‘stimulus”’ of the wound. The same 
may be said for the growth of roots in the main stem of the plant, 
which may take place several inches away from the seat of injury. 
We need not dwell on this point any further, since this is generally 
conceded. It is chiefly in animals that we find regeneration local- 
ized at the wound; but this is apparently due to the fact that in 
such animals any cells may give rise to new growth, while in 
Bryophyllum calycinum the power of giving rise to shoots is 
restricted to buds located in definite places in the plant. 
II. Isolation as the cause of regeneration 
It is generally stated that ‘‘isolation”’ is responsible for regenera- 
tion, inasmuch as isolation would release the leaf from the inhibit- _ 
ing influence which the whole has on each part.’ It is obvious, 
however, that isolation is an abstract term and that it cannot help 
us, therefore, in visualizing the forces inhibiting the growth of the 
buds while the plant is intact. We will show in a simple example 
that the conception of isolation, while it may fit some cases, will not 
fit others. 
The following experiment was often repeated during the winter 
months. Three leaves of the same plant of Bryophyllum were 
suspended in an aquarium saturated with water vapor, so that 
the tips of the leaves (or about one-half of each leaf) were sub- 
mersed in water at the bottom of the aquarium (figs. 1, 2,3). Leaf 
I was completely isolated from the stem; leaf 2 had a piece of a 
stem of the plant attached; and leaf 3 had in addition to a piece of 
the stem of the plant also the opposite leaf attached. The draw- 
ings show the condition of the three leaves after 11 days. Leaf 1 
formed roots in a few days, and soon after shoots at the notches of 
the submersed part of the leaf. In leaf 2, as a rule, all growth from 
the notches was inhibited, but the bud of the stem opposite the 
leaf grew out very rapidly into a shoot (fig. 2, 5). The submersed 
part of leaf 3 again formed roots and stems in its notches, not quite 
but almost as quickly as leaf 1. Experiments showed that the 
, C. M., Die physiologische Isolation von Teilen des Organismus, etc. 
Roux’s ‘Vr wed Aufsitze. Leipzig. rgrt. 
