May, 1902 .] Galls and Insects Producing Them. 
269 
The inner zone shows a marked resemblance to H. centricola 
(Fig. 27). The subdivision into protective and nutritive parts in 
my specimens was not like the characteristic zones described by 
Fockeu ; the inner cells were apparently much thicker walled and 
more indefinite. However, I believe that younger galls would 
have shown the typical characters. The outer zone is thicker 
than in either H. centricola (Fig. 27) or A. inanis (Fig. 28), but 
not so thick as in C. tumifica (Fig. 26). It can be readily sub- 
divided into epidermis and parenchyma and it also shows a fairly 
well defined endodermis, and in that respect differs from either 
H. centricola or A. inanis. 
Callirhytis papillatus O. S. (Fig. 30 a. b. c.), which is similar 
to the preceding Cvnipidae galls, but shows considerable varia- 
tion from them. It is smaller than any of the preceding and is 
embedded in the leaf very similar to C. tumifica (Fig. 26). The 
two zones are separated, the outer being similar to A. inanis 
(Fig. 28), the inner zone surrounding two or three larval cham- 
bers instead of one. Next to the larva the cells are very large 
and thin and may be considered nutritive ; outside these we have 
well defined parenchyma or protective cells, and outside these we 
have two or three layers of cells well filled with protoplasm. The 
connection between the outer and inner zones is by single elon- 
gated cells, which are very rich in protoplasm. 
The evolutionary development of the preceding Cynipidae galls 
is evident. All show the two well defined zones, the outer non- 
staining made up of epidermis and parenchyma and the inner 
which takes the stain readily and is made up of two subdivisions, 
protective (or sclerenchyma cells) and nutritive (or parenchyma 
cells). In C. tumifica (Fig. 26) we have the two zones in con- 
tact ; in H. centricola (Fig. 27) and in A. inanis (Fig. 28) we 
have a separation of the two zones which are now connected by 
fibro-vascular bundles ; in C. papillatus (Fig. 30) the two zones 
are connected by long, undivided cells ; in D. palustris (Fig. 29) 
we have a complete separation of the two zones. 
With the exception of N. irregularis (Fig. 25) and C. tumifica 
( Fig. 26) they all show a division into four zones as described by 
Fockeu. However, Fockeu does not describe a separation 
between the parenchyma and protecth T e zones which is so charac- 
teristic of some of our American galls. I am inclined to consider 
our American Cynipidae galls as having reached a higher stage 
of development than the European forms. 
The larva in all species evidently draws its nourishment directly 
from the inner zone. I11 H. centricola (Fig. 27) and A. inanis 
(Fig. 28) the inner zone evidently gets its nourishment through 
the fibro-vascular bundles ; in C. papillatus ( Fig. 30) the supply 
of nourishment comes through the long filamentous cells ; in 
D. palustris (Fig. 29) it is probable that the larva is far advanced 
