Dec, 1915] Zoocecidia on Species of Hicoria 39 



growing tissue of the immature leaf. Nothing has yet been 

 done on the development of the itonid galls of the hickories, 

 but from studies on very similar types we have reason to believe 

 that the ontogeny of the itonid forms is as follows: The egg 

 is probably deposited superficially (for the ovipositor of the 

 female Caryomyia is short) on the under side of the leaflet; on 

 the upper side in a few cases. 



Hyperplasia or excessive cell proHferation results (probably 

 not until after the larva has emerged from the egg) forming 

 at first a saucer-shaped structure, then cup-shaped and finally 

 by the ingrowth of the edges, the gall becomes a closed structure 

 enveloping the larva in a chamber. The distal growth, seldom 

 if ever in the hickory forms, proceeds so far as to obliterate the 

 opening which was so prominent in the very immature cup- 

 shape stage. Hence in practically all galls of this type a 

 minute canal or pore can be demonstrated at the distal end. 

 In Kiister's* very serviceable classification of abnormal plant 

 parts, these fall under his " umwallungen " cecidia, a term 

 very succinctly describing their mode of development. 



Two of the following described galls have been studied 

 histologically by Cook,t Caryomyia holotricha O. S. and C. 

 tubicola O. S. 



Concerning the problem of the distribution of the galls on 

 the different species of hickory, it is still too early to be able to 

 make any positive assertions. In most of the reports the 

 species of tree has not been given. It is very well known that 

 certain species of galls are found on 2 and 3 species of hickory, 

 but whether they are developed on all indiscriminately is not 

 known. H. cordiformis seems to bear much fewer species 

 than H. ovata or //. alba. In the present list, the report of 

 the gall upon a particular species of tree does not at all imply 

 that it does not occur on others. 



Having had the opportunity to give attention to gall col- 

 lecting in three rather widely separate localities, eastern 

 Connecticut, southern and northern Ohio and eastern Kansas, 

 some observations on the geographical distributions of the 

 hickory itonids are here briefly presented. 



*Kuster, E. Die Gallen der Pflanzen, Leipzig. 1911. 



tCook, Mel T. "Galls and Insects Producing Them." Ohio Nat. 4:140-141. 

 1904. 



