1918] LOEB—CORRELATION I51 
equal size without a leaf attached to it will in the same time form 
no shoot or only a very tiny shoot (fig. 3). The inference was drawn 
that the inhibiting effect of the stem upon the leaf in fig. 2 was due 
to the fact that the leaf furnished the material required for the 
growth of shoots to the stem instead of to its own notches. This 
takes place even when no shoot is formed in the stem; in that case 
the material furnished by the leaf is stored in or consumed by 
Fic. 1 Fic. 2 Fic. 3 
Fics. 1-3.—Figs. 1, 2, sister leaves; leaf of fig. 2 still attached to stem, showing 
stem inhibits shoot formation in leaf; fig. 2 shows inhibition is accompanied by 
accelerating effect of leaf upon growth of shoot from stem, since in a piece of stem, 
suspended in moist air, as in fig. 3, production of shoots is suppressed or retarded. 
certain cells of the stem, as indicated, for example, by callus for- 
mation and by geotropic curvature.‘ 
The same principle was shown to hold if stems without leaves 
are suspended in moist air. In such cases the two buds of the 
most apical node of a long piece of stem grow out (fig. 4), and 
it can be shown that the basal part of the stem whose buds are 
inhibited from growing furnishes to the growing buds at the apex 
‘Logs, J., Science 46:547. 1917. 
