140 
The Ohio Naturalist. 
[Vol. IV, No. 6, 
APPENDIX I. 
GALLS AND INSECTS PRODUCING THEM. 
Melviu.e Thurston Cook. 
Part I. Morphology of Leaf Galls. 
I. GALLS OF THE APHIDIDAE. 
The gall of Pemjjhigiis vagabuiidus Walsh (Fig. 112) is evi- 
dently formed as a result of the distortion of a large number of 
bud leaves. My specimens of these galls were mature, so I was 
unable to follow its development. Small fibro-vascular bundles 
were numerous and tannin was formed in great abundance. The 
structiire was so modified that the leaf characters were lost ; the 
cells were uniform in character, but were slightly smaller near 
both the exterior and interior surfaces. 
The galls of Pemphigus rhois P'itch (log. 113) are large, blad- 
dery and evidently the pocketing of a single leaflet of the host 
plant, Rhus glabra or R. typhina. My specimens of these galls 
w'ere fully mature, and I was therefore unable to follow the line 
of development. The leaf structure was modified into the char- 
acteristic Aphididae gall structure. F'ibro-vascular bundles were 
numerous and near the inner surface of the gall. Opposite each 
bundle was a large cavity filled with some substance which I was 
vinable to determine. 
2. GALLS OF CECIDOMYIDAE. 
The galls of Cecidomyia pellex O. S. (Figs. 114a, b) are formed 
by a thickening of the petiole, giving it the appearance of a long 
fleshy bean pod with a slit along the upper side. This gall shows 
three well defined zones ; an inner nutritive zone of small cells, a 
parenchyma zone of larger cells and the epidermal zone. The 
fibro-vascular bundles are numerous and are located between the 
nutritive and protective zones and arranged around the larval 
cavity and opening, the largest one just below the larval chamber 
and corresponding to the mid-rib of the leaflet. 
Cecidomyia impatientis O. S. (Fig, 115) is a fleshy gall occur- 
ring on the leaves of Impatiens fulva. Some of my specimens 
had the appearance of deformed flower buds, but upon this point 
I was unable to decide. This gall .showed two well defined 
zones ; a zone of small cells lining the larval chamber and making 
up about one half the thickne.ss of the gall, and an outer zone of 
large cells. Small fibro-vascular bundles were formed between 
the zones. 
The galls of Cecidomyia holotricha O. S. on Hicoria ovata 
(Figs. ii6a, b, c) are small and very firm. My specimens were 
