THE GALL OF THE MONTEREY PINE. 
W. A. CANNON. 
ONE species of pine, the Monterey pine,! which is especially 
abundant in the arboretum of the Leland Stanford Junior Uni- 
versity, has recently been so seriously affected by a gall that 
the beauty of a great number of the trees has been greatly 
impaired, and their total destruction made probable. The gall 
is caused, as was first observed by Mr. W. A. Snow,? by larve 
of a gallfly belonging to the family Cecedomyiide. 
The gall consists of a malformation of the leaves and !eaf 
bases. The galled leaves vary in length from .5 to 1.5 cm., 
and their bases are so badly swollen that the leaves are often 
pear-shaped. The larva live in pockets in the swollen leaf 
bases. The gall occurs on the youngest leaves, and for that 
reason leaves containing larve are to be looked for at the tips 
of the branches. Where the same branches have been galied 
several successive seasons their tips appear as if closely clipped 
and look like great bottle brushes. The galled leaves do not 
remain so long on the tree as the normal ones. 
If one of the galled leaves be examined the autumn after it 
has been stung, it will be found to contain in its base four or 
more larva. These are without biting mouth-parts, but they 
are none the less completely enclosed by plant tissues. It 
was to learn, primarily, how the larva got inside of the leaf 
base, and also to trace the immediate cause of the hypertrophy, 
that this study was undertaken. To these were added, in the 
course of the investigation, other questions of physiological 
interest, 
l Pinus radiata D. Don., Trans. Linnean Soc. vol xvii (1836), p. 441; 
formerly known as Z. insignis Loudon, Arb. Brit, vol. iv (1838), pp. 2265, f., 
2170-2172. 
? This study was taken up with Mr. Snow, since deceased, and subsequently 
carried on by Miss Helen Mills. Zhe Entomological News, vol. xi (1900), p. 489. 
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