1904] PEIRCE: THE MONTEREY PINE 455 
are similar. Normal seedlings and normal-leaved pine branches 
develop bundles of normal proportions, while amputated seed- 
lings and branches bearing galled leaves develop bundles which 
vary from the normal according to the degree of injury which the 
leaves have undergone. In the case of Jost’s seedlings the con- 
sequences of amputation are clear. That they are the results of 
any one set of factors is by no means clear. In the case of these 
Monterey pines we have plants which are also profoundly although 
gradually influenced by the treatment to which they have been 
subjected. No wounds are produced by the gall-fly depositing 
its eggs at the bases of the young pine needles, there is no sud- 
den shock to the whole plant, and there is no sudden or great 
change in the weights, or the position of the weights of the 
leaves, The galled leaves have less area and less chlorophyll- 
containing tissue than normal leaves, they lose less water 
by evaporation and contribute less food to the plant as a 
whole than normal leaves do. They may consume more food than 
normal leaves, but this is by no means certain. The products of 
the gall-larvae—excreta of various sorts—certainly affect the 
leaves at the bases of which they live and it may be that these 
substances are carried to considerable distances and affect the 
growth of the tissues in the branches. But of this there is no 
evidence unless we assume that these excreta affect only the 
young cells of the xylem. It seems to me reasonable, therefore, 
to conclude that it is principally the reduced surface from which 
water is evaporated, and that the decreased food-manufacturing 
tissue is only a minor cause, to which the smaller amount of 
wood and the narrower annual rings can beattributed. We have 
then in this pine a confirmation of Jost’s conclusions that leaves 
and vascular bundles are closely correlated in their development, 
a confirmation the more interesting because it is furnished by 
gradual change rather than by sudden and shocking influences, 
by influences which operate out of doors, under natural condi- 
tions, where there can be no suspicion that the results are due to 
more or less obscure laboratory causes. 
STANFORD UNIVERSITY, 
California. 
