168 BOTANICAL GAZETTE [FEBRUARY 
remains in the leaf and becomes available for the notches. As a 
consequence the notches in the leaf begin to grow out. The chances 
for growth are apparently not equal for all the notches of a leat 
suspended in moist air, but are as a rule better for those in the 
middle of the leaf, where the leaf is thicker and where probably 
more sap is available. The roots grow out before the shoots begin 
TABLE XI 
FEBRUARY 15—MARCH 20, 1917 
Sister leaves a of Iysdangy bg bas red ears SS bey 
I {{8} @ WAIVeS. 366355. 3 0.316 1.866 170 
"TO} 36 pieces, 04. 14 0.345 1.927 200 
Il f(a) Whole leaf... ... 4 ©.490 2.061 233 
: SY ta pretes 14 ©.312 1.810 172 
Ill 1s Whole leaf... ... 2 0.450 4.465 100 
TACO) 27 PIBCES 2 ck ks. 15 0.300 2,57 95 
Whole or half 
CAVES. Co. os 9 1.256 8.392 150 
Averages Leaves cut into 
small pieces ... 43 ©.057 6.71 143 
to grow. Those shoots which happen to grow out first now become 
a center of attraction for all the material available for growth in the 
leaf, and they thereby inhibit not only the growth in most of the 
other notches but actually cause the roots formed in other notches 
to dry out again, as a comparison of fig. 12 with fig. 11 shows. We 
cannot yet tell how it happens that the more rapidly growing leaf 
attracts the sap to itself. 
We have mentioned that as a rule the notches which will grow 
out first are not the ones at the apical or basal ends, but in the 
middle of the leaf, where the leaf is thickest and where apparently 
more sap is available. That it is possibly only the quantity of 
water which decides the initiation of growth® is suggested by the 
fact that a leaf, like the one in fig. 12, which, when suspended in 
moist air forms no shoots in the apical notches, can be caused at 
§ This refers only to the initial step of starting the growth in a dormant bud; its 
actual growth, of course, depends upon the supply of sugar, amino acids, salts, and 
other solutes from the leaf. 
