810 THE AMERICAN NATURALIST. 
IV. 
I have been asked, why does not this gall attack other spe- 
cies of pine? and it may be said that one other species, of half 
a dozen that were examined which are growing in the Stanford 
University arboretum (Pinus attenuata), has a few galled leaf 
bundles. The young shoot of this pine is, early in the growing 
season, similar in structure and size to that of the Monterey 
pine, but the leaves of P. attenuata do not remain the right 
length for being visited by the gallfly long enough to be seri- 
ously injured by it. The other species of pine do not develop 
their shoots at the right time, or the shoots are covered with 
resin, or they are otherwise unfitted either by size or by struc- 
ture to be galled. The opinion may be ventured that the con- 
ditions for the proper laying of the eggs and those governing 
the life of the larvæ are so delicate and exacting that other 
species of our pines are not likely to suffer from the parasite. 
The materials for this paper were collected in the spring and 
summer of 1898, from galled Monterey pines which were grow- 
ing in the university arboretum. 
LELAND STANFORD UNIVERSITY, 
PALO ALTO, CAL 
