1918] LOEB—CORRELATION 153 
grow out first inhibit the growth in the other notches. (No part 
of the leaf of Bryophyllum calycinum except the notches is able to 
give rise to shoots or roots. The formation of roots will be omitted 
from consideration in this paper in order to simplify the discussion.) 
Our contention is that this inhibition in leaf 6 is due to the absorp- 
tion of all the material available for shoot formation by the 4 
notches that happened to grow out first, thus depriving the other 
notches of the material needed for the growth of shoots. By 
comparing figs. 5 and 6 it will be noticed that 3 of the shoots which 
leaf 6 produced are considerably larger than the individual shoots 
VY nara oe “4 
BO Se 
ZSs 4/ 
Fic. 5 . Fic. 6 
Fics. 5, 6.—Sister leaves: fig. 5, leaf cut into as many pieces as notches; almost 
every notch forms a shoot; fig. 6, leaf intact, only 4 shoots formed, 3 being considerably 
larger than those shown in fig. 5, thus indicating tendency of both leaves to produce 
equal masses of shoots, although number of shoots may vary considerably. 
of leaf 5, and this suggests the possibility that the isolation of a 
piece with one notch simply prevents the material needed for the 
growth of the notch being taken away by some of the other notches 
which by chance start growing a little earlier. 
In order to prove this we must be able to show that if we isolate 
two sister leaves (which are of equal size, age, and history) and 
keep them under equal conditions, they will produce in equal times 
approximately equal masses of shoots. It is necessary, of course, 
that both leaves are healthy and not yet beginning to etiolize, and 
that they should not do so during the course of. the experiment. 
