1918] LOEB—CORRELATION 165 
In spite of the enormous difference in the number of shoots in both 
cases, the weight of shoots produced by one gram leaf in a given 
time was not very different, the average being 143 mgm. of shoots 
in one set and 150 mgm. in the other set per gram of leaf. 
The law of equal production of shoots by equal masses of leaves 
explains why the shoots growing out from the notches of a leaf grow 
the more rapidly the smaller their number. It does not explain 
TABLE X 
SISTER LEAVES: (a@) WHOLE LEAF, BUT ALL NOTCHES WITH EXCEPTION OF 
(b) CUT INTO 4 PIECES, BUT NO NOTCH REMOVED; APRIL 4—APRIL 25, 1917 
Sie | Oe ee ac 
L 1 we jpirve apes he as I 0.201 2.202 90.5 
O) 8 eens. 6 0.316 2.542 124 
II. {(o Whole leaf. . I ©.144 - 2.0325 7 
(b) 4 thems. 2 4 0.2335 2.3235 100.5 
III. {is Whole leaf... ... I Enea 1.832 88 
\b) 4 pheeee. es As 0.179 T.950 92 
IV. i bide as pees I 0.147 2.152 
(b) a-paeces.. 3. .: 4 0.256 2.5145 102 
V. 103 Whole leaf... ... I 0.150 2.710 55 
(0) 4 pleces. 6... 4 “0.191 2.667 72 
VIL 13 Whole eats. |: I 0.084 0.986 85 
(a peewee: i oe os 4 o.1II 1.107 100 
Total number of Total weight of | Total weight of | Shoots per gm. 
shoots shoots leaves of leaf; mgm. 
7 (a) Whole leaves. 6 0.8889 IIl.QI5 74.5 
erin ph 1 Cut leaves ... 26 1.2875 13.104 98 
how it happens that in an isolated leaf not all the notches grow out 
into shoots. 
When we cut off a leaf and suspend it in moist air (the air not 
being completely saturated with water vapor), after some time most 
of the notches form roots, as the leaf in fig. 11 indicates, which was 
drawn 18 days after the beginning of the experiment. If there are 
any notches which do not form roots, they are usually found at 
the apex and at the base of the leaf (fig. 11). After the roots are 
