75 
Léw. They occur on the upper surface of the leaf (usually on each 
side of the midrib) in small numbers, and resemble rifie-bullets 
in form. They are} x zx inch, green at first, becoming brown, 
apparently smooth, but really covered with adpressed short hairs 
which are said te become erect when the gall is mature, but I 
have never seen them so), walls thin, and composed of compact 
tissue. On the lower surface they are covered with a raised scale- 
like piece of epidermis. When mature they fall off, leaving scars 
on the leaf, and the midge appears next year. The galls are com- 
mon in autumn near Aberdeen, at Banchory, at Parkhill, at In- 
verurie, &c. 
Corylus Avellana L. (Hazel). The galls are leaf-buds which become 
swollen, rounded, }-2 inch in diameter, with enlarged imbricate 
leaf-scales, and abortive leaves, all covered with a thick coating of 
greyish-white, transparent hairs, among which live multitudes of 
mites—Phytoptus (= Calycophthora Avellane Amer.). The galls 
are mostly at or near the ends of the twigs. They are abundant 
at Banchory in May and June. 
Nat. Ord. BETULACER. 
Betula alba L. (Birch.) 
A. 
Swellings on the midribs, including the origins of the chief 
veins, and most conspicuous below, = Sih i> inch, nearly cy- 
lindrical, but pointed at both ends, smooth, wall thin, cavity 
large, inhabited by a whitish larva of a Cecidomyia? They occur 
in Braemar, and in the Parkhill woeds, rather sparingly in autumn. 
B. A blister of the lamina, projecting on both surfaces so as to form 
a pretty large cell. The galls are usually connected with the mid- 
rib, or with one of the large veins, are round, 33;-§ inch in diameter 
by oe * inch deep (but frequently two or three are united), surface 
covered with short hairs like the rest of the leaf. ‘The colour above 
is green, in the centre surrounded with a purple ring, below green 
only; walls thin. Each is tenanted by a larva of a Cecidomyia, 
which leaves the gall when mature by a small hole through the 
lower surface. The galls are common in July at Banchory, in 
Braemar, in Parkhill woods, at Braes of Gight, &c. 
c. Buds at the tips of the branches, swollen, and tenanted by larve 
D. 
of Cecidomyia. Not uncommon on the same bushes as the last. 
Bud-galls of Phytoptus. They are buds the leaf-scales of which be- 
come greatly enlarged (as in the Hazel) owing to the attacks of 
mites, the leaf-scales also become covered on both surfaces, except 
near their base, with a thick coat of silky adpressed hairs. The 
bud thus becomes much larger than the normal size (reachingj{ 
inch, or more, in diameter), and loses entirely its glossy appear- 
ance, so that it is readily observable, especially after the fall of the 
leaf. Under the microscope the basal part of each scale is found 
to be covered with small spherical papille. Multitudes of whitish 
mites are to be seen, especially between the central leaf-scales. 
The galls occur singly, or there may be several on a branch, and 
ultimately there result from the irritation thus caused the ‘ Witch- 
knots,’ so frequent on birches everywhere. Miss Ormerod was the 
first to point out the cause of these curious growths (Entomologist, 
X., 83-86, with figures). ‘ 
Leaf-galls caused by Phytoptus. These are scattered over the 
lamina, sometimes to the number of 50, or more, on a leaf, usually 
