On leaf, generally on upper side, balloon-shaped gall, 3-5 mm. high,
3-4 mm. wide. Terminal nipple arising from slight apical depression.
Greenish-brown or sometimes varying toward a very dark purplish tinge,
its peculiar color being very constant and characteristic. The surface
is dotted over with short, swollen glandular hairs. Trichomes sometimes
projecting slightly from apical pore. Walls very thin. Galls attached
to short, stout process of the leaf, to be seen only in median,
vertical section. Surface of leaf on side opposite the gall not raised.
Never numerous on leaflet. Closely related, if not identical, with
_C. caryae_ O. S. See No. 20.
Observed on _H. glabra_, in Hocking County, Ohio, July.