On leaf, under side, sub-spherical gall with more or less prominent
apical nipple. 3-3½ mm. diameter, rarely 4 mm. Light green, turning
brown, smooth. In many, very definite meridian-like striations can be
observed marking the wall. Wall thin, very fragile and dry. Surface of
chamber smooth as though polished. Attached by conic pedicel arising
from fovea in base of gall. This pedicel with its pointed end attached
to the leaf is surrounded by or rests in a cup-like structure. In this
respect the gall differs markedly from No. 22, which it superficially
very much resembles.
Fig. 20a is a large specimen showing the peculiar interlocking base
exceptionally well developed.
Collected from _H. alba_ and _H. ovata_, July and August.
Felt, Jour. Econ. Ent. 4:456. 1911.