312 BOTANICAL GAZETTE [ NOVEMBER 
ment, while in reality they are still polystichous, like the leaves 
on the terminal shoot. 
The . elatinum witch broom on A. balsamea differs from | 
that found on A. pectinata and A. firma, in that it seldom has 
normal branches growing together with the diseased ones above 
the tumor. The diseased branches are also more numerous, but 
correspondingly smaller. With the increase in height of the 
tree, the lower normal branches and the affected branches soon 
die on account of an insufficient amount of light. The witch 
broom dies with them, since it is dependent on the normal host 
for its food supply. 
Although that part of the witch broom branch below the 
tumor is not diseased, its annual growth in diameter is less than 
in normal branches of the same age. The supply of food is 
transported to the witch broom, which grows at the expense of 
the normal parts of the host. This increased growth of the 
witch broom makes it much heavier than the normal branches, 
so that it is usually found suspended from larger limbs of the 
tree, or hanging near the tree trunk when the whole branch is 
affected. The living and actively growing ones on older trees, 
excepting where the trees are isolated, are always found near the 
top, where there is a sufficient food supply. Although photo- 
synthesis is almost entirely absent in the witch broom, it is 
extremely sensitive, and dies from an insufficient amount of light. 
As to the size of the witch broom on A. balsamea, the avet- 
age diameter is from 15 to 30°, and the length from 20 to 6" 
Ill. ANATOMY OF THE NORMAL AND DISEASED LEAVES. 
1. Normal leaves—The leaves of Abies are sessile, and with- 
out the prominent pulvini peculiar to the spruces. The leaves 
of the lateral branches of A. dalsamea are more or less flattened, 
notched, or obtuse at the tip, grooved on the upper sur face and o 
5 Picea nigra, which grows with A. da/samea in the bogs of northern Minow es - ae 
often has a witch broom 40 to 90% in diameter. The broom is caused by ap esac aS Roc ea 
in the number of branches, the internodes of which remain shorter than in me — e eee 
This witch broom is not caused by -&. eatinum, but by some other fungus or ami poe 
(Compare v. Tubeuf, Forst-naturw. Zeitsch. — :76. p/. 5. 1893- ee | 
i 
: ae 
