May, 1902.] Galls and Insects Producing Them. 269 



The inner zone shows a marked resemblance to H. ceutricola 

 (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. ceutricola (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. ceutricola or A. inanis. 



Callirhytis papillatus O. S. (Fig. 30 a. b. c), which is similar 

 to the preceding Cynipidae 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. ceutricola (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 b}- 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 protective 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. In H. ceutricola (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 



