1904] PEIRCE: THE MONTEREY PINE 449 
fly. In addition to these, field mice and other animals, whose 
depredations were concealed and facilitated by the long grass which 
was allowed to grow among the trees for a few years, made the ~ 
already unfavorable environment almost unbearable. In various 
respects, however, conditions in the arboretum have improved. 
Even at Pacific Grove,in a natural forest, this pine is just now 
having a hard struggle for existence. Conditions in this bit of 
forest have been considerably changed of late years, paths and 
roads having been cut through it, and a few years ago a serious 
fire swept over part of it. This forest is extremely important, 
for it is the main protection of the town of Pacific Grove against 
the sand which, now piled up in magnificent dunes, would other- 
wise be blown inland and over the town. It is still too early to 
determine whether the effort now sic made to save this forest 
will be altogether successful. 
The evident sensitiveness of these two trees, the redwood 
and the Monterey pine, is interesting in connection with their 
limited distribution. The redwood seems to be confined to the 
fog belt, the Monterey pine to only a small part of this. Mois- 
ture in the air is apparently the principal limiting factor, but the 
still further limiting one in the case of the Monterey pine is not 
evident. Seeds of this pine are now being extensively distributed 
for purposes of experiment. Whether it will prove under these 
new conditions to be more widely successful than it has hitherto 
been is a question of great theoretical as well as practical 
interest. 
Turning now to the leavesof Monterey pines which have been 
attacked by the gall-fly, Diplosis, we shall see, in addition to the 
characters described by Cannon, certain other significant differ- 
‘ences from normal leaves. At the same time that there is a 
very considerable thickening of the leaf throughout its length, 
but especially at the base, the leaf-surface is greatly decreased. 
The average diameter of 20 normal leaves one year old is 
0.735™™, as measured by micrometer caliper, and the length 
94.8™™. The average diameter of 20 galled leaves one year old 
ranges from 1.72™™ at the base to 0.62™™ at the middle, and the 
average length is 19.5™™. The shape of all these leaves is far 
