1918] LOEB—CORRELATION 173 
It is obvious that in both cases the shoot formation is con- 
siderably greater in the light than in the dark. The experiment 
seems to indicate that either the process of assimilation contributes 
directly or indirectly to the formation of material for shoots in the 
_ leaf, or that the light in some other way contributes to the shoot 
formation. It is obvious that among the conditions which are to 
be considered in the production of equal masses of shoots by equal 
masses of leaves equality of illumination is of special importance. 
The writer observed deviations from the rule of equal production of 
shoots by equal masses of sister leaves when the leaves were able 
to partially cover or shade each other. 
TABLE XII 
SHOOTS PRODUCED 
WeEIcHT or /|Mem. or sHoots 
LEAVES IN GM. |PRO GM. OF LEAF 
Number Weight in gm. 
I. 6 pairs of leaves sus- 
pended in moist air in 30 days 
os GME oie gees 3 0.016 11.65 
ee ee 24 0.543 8.03 68 
Il. 7 pairs of leaves dipping 
in wi in 26 days 
7. tuk his Oe eet 14 0.406 53.377 30 
Be WO. ei: 17 1.725 17.270 100 
In this paper we have considered only the production of equal 
masses of shoots by equal masses of sister leaves of Bryophyllum 
calycinum. The law is probably correct for leaves of Bryophyllum 
in general, provided a sufficiently large number of leaves are com- 
pared, so that the influence of individual differences in the leaves 
(age, amount of chlorophyll, etc.) is eliminated. 
It is also very probable that this form of correlative inhibition 
of growth is not confined to the leaf of Bryophyllum, but is a more 
general phenomenon. Thus it seems to exist in the potato, where 
the growth of one bud seems to inhibit the growth of other buds of the 
same tuber, and perhaps for reasons similar to those set forth here. 
Summary 
1. Equal masses of sister leaves produce approximately equal 
masses of shoots in equal time and under equal conditions, even if 
the number of shoots varies considerably. 
