138 A Botanical Study of the Mite Gall [ February, 
supplied their place but mainly compose that part of the gall that 
is made up of folded tissue. Two or three layers of the pitted 
cells near the pith are wider than long and regular in shape. 
As the distance from the pith increases the cells increase in 
length and decrease in breadth until they are two or three times 
longer than broad. Owing to the crowding to which they are 
exposed, they become irregular in shape nearer the surface of the 
fibro-vascular bundle. 
In the normal petiole the cells overlying the fibro-vascular 
bundle are longer than broad, regular in shape and contain but 
little protoplasm. The corresponding part in the galls is made 
up of much larger cells, irregular in form and filled with a granu- 
lar substance which is slightly colored yellow by iodine, and red 
by eosin. 
Clustered and glandular hairs are found irregularly distributed 
over the petiole. The clustered hairs (Fig. 6) are found abun- 
dantly on the upper side of the petiole near its base. From this 
point their number decreases though there are still more on the 
upper side of the petiole than on the lower. They originate from 
cells of the epidermis which have crowded together in papilla- 
like masses, But one hair arises from each cell. Each papilla 
may have but one hair, though it will often have nine or ten. 
The ordinary number is five or six. The hairs themselves are 
one-celled and pointed toward the apex. At the extremity their 
walls are so thickened as to nearly obliterate the cavity. They 
are thinner towards the base, and iodine shows protoplasm to be 
present. 
The glandular hairs vary in shape. Ina general way they are 
made up of several cells, the terminal cell being larger than those 
below, and secreting an “acrid aromatic” substance. Iodine 
shows that there is protoplasm in their cells. These glandular 
hairs arise from single epidermal cells which are separate from 
each other by two or three intervening cells, 
The galls have no differentiated epidermis. Certain cells which 
from their position would be called epidermal are without proto- 
plasm, but in other respects resemble those beneath. From 
nearly every one of the epidermal cells cylindrical, one-celled 
hairs arise (Fig. 8). These hairs seem to be a continuation of the 
epidermis, They are about 1™ in length and ṣẹ ™ in diameter, 
that is, at least twice as long and broad as the normal hairs. 
