Dec, 1915] Zoocecidia on Species of Hicoria 51 



nipple. 3-5 mm. vertical diameter, 3-5 mm. wide. Interiorly 

 the chamber of the isolated form is depressed, this fact being 

 associated with that of the thick distal wall. Gall chamber 

 surrounded by definite sclerenchyma layer. Cortical tissue 

 firm. Attached by irregular process from leaf extending into 

 base of gall. In the massed forms, the galls are similar in 

 structure, but are variously shaped, due to mutual pressure, 

 (Fig. 21b). Compactly attached to the common central 

 hyperplasia along the vein, which on the upper side of the leaf 

 is a reddish irregular, low elevation. Some of these masses are 

 as long as 5 cm., possessing a thickness of 10-15 mm. 



Common on various hickories, particularly H. ovata. 



A gall which may eventually prove to be a difi^erent species 

 but which here is provisionally classed as a variety of C. holo- 

 tricha, was found in numbers on the leaves of H. alba, though it 

 is probably not restricted to this species of hickory. Instead of 

 an apical nipple, it has an apical pit, which is choked with the 

 characteristic brown pubescence of this type of gall. Internally 

 a tuft of coarse brown trichomes extends inwardly from the 

 distal side of the chamber. The chamber occupies the proximal 

 one-half to two-thirds of the gall, the wall over it being uni- 

 formly very thick. This type of gall is constant, being col- 

 lected repeatedly and examined minutely. 



Based on Felt's brief description, his Caryomyia thompsoni 

 Felt was taken from this gall or one very similar to it. 



Closely allied to the above variety is another form, with 

 internal tuft of trichomes, in which the apical nipple is present. 

 The layer of tissue lining the chamber appears very white, due 

 probably to the character of the tissue beneath the superficial 

 nutritive layer. In section the thin white chamber wall is very 

 definitely delimited from the adjoining darker tissues. Many 

 of these conic-sub-spheric galls were 6 mm. in width. Collected 

 on H. glabra. Types of this and the above variety are at the 

 Ohio State University. 



Osten Sacken, Lowe's Monogr. Dip. N. Am. Pt. I, p. 193. 1862. 



Felt, "Hormomyia holotricha" 23rd Rept. Ins. N. Y. 1907. pp. 382, 389. 



Felt, "Caryomyia holotricha" Jour. Econ. Ent. 4:456. 1911. 



22. Cecidomyia sp. Cecidium nov. 



On leaf, under side, sub-globular with minute apical nipple. 

 Tip of latter truncate with fine pore in center. 3 mm. high, 

 2/^-3 mm. wide. Generally wider through one axis. Smooth; 



