1918] LOEB—CORRELATION 169 
any time to form new shoots in these notches if we let the apex dip 
into water. As soon as this happens these notches will form shoots 
and these shocts will soon equal or exceed in size the old stems, and 
in turn may now inhibit the growth of the latter. 
The leaf in fig. 12 was drawn on January 30. On February 7 
its apex was suspended in water and soon new shoots formed in the 
apical notches (figs. 13,14). Fig. 13 was drawn 9 days, and fig. 14, 
leaf was aon with apex in water mit now new shoots are formed in tered notches, 
which grow rapidly and soon reach size of two original shoots; proves that amount 
of water determines which notches shall grow into shoots. 
16 days after the apex was put into water. It will be noticed 
dipping in water. This never happened when the leaves remained 
in moist air. It can be shown that such a leaf when dipping in 
water absorbs water, and we are justified therefore in assuming that 
the increase in the contents of water in a notch or the starting of a 
current of water through the notch starts its growth. 
We may compare the conditions for the initiation of the growth 
of a notch in a leaf to those of the growth of a seed, inasmuch as in 
both cases an absorption of water is necessary to initiate growth. 
