i 
194] COPELAND—VARIATION OF CALIFORNIA PLANTS 403 
at most a small and homogeneous group subject to a common impulse. 
We are in the habit of thinking of variations as concerning entire 
organisms. 
More frequently, however, such leaf forms as these are not so 
strictly characteristic of whole trees; but single twigs show uniformly 
aberrant types of leaves; or most often single or few leave’ of diver- 
gent forms are found scattered over the tree. Fig. 2, a represents the 
leaves of a single twig on which the leaf character changed profoundly 
during the season. This might have been ascribed to a change in the 
available water during the season, but that not all the twigs of the tree 
0OOD)0000 000000 
* 2-—Quercus chrysolepis: a, all the leaves of a twig; b, younger leaves of a 
Bo itive leaves; d, some leaves on one season’s growth of a twig. 
Fic 
twig; ¢, 
so mn this way. ig. 2, b shows the opposite change in the same 
hg wth, on another specimen from Chico; and jig. . C, 
OW ab Ing four successive leaves on one twig of the same tree, s os 
2, a 4 the size, as a character of the twig, may cUAnRe: : * 
twig. i * Outlines of a number of leaves on one season 7 growth o : 
meriste a “ase variation seems to have occurred not in the ae 
idvidual ie” tise to both axis and leaf, but in the primordia of the 
eaves, 
QUERCUS pDuMosa Nuttall. 3 
€ figured leaves of Q. dumosa were collected in a single 
of chaparr al, on exposed parts of mature shrubs; their 
are therefore independent of the environment. Fig. 
all the leaves of the last season’s growth on two twigs of the 
All of th 
‘mall Patch 
“ferences 
3, a~h are 
weed 
