268 The Ohio Journal of Science [Xo\. XVI, No. 7, 



related to the origin of the structure, for the embryonic tissue 

 concerned in its development never was related to the pro- 

 cambial strands, but was entirely new hyperplasia tissue. The 

 pores leading from the chambers through the core are lined 

 with short multi-cellular trichomes. (Fig. 7g). 



Fam. Itonidid.e (Ord. Diptera). 



This family, formerly known as the Cecidomyiidse, embraces 

 a large assemblage of gall makers. In the vast majority of 

 cases, the egg is deposited superficially on the very young 

 plant parts. The gall does not begin development until the 

 larva hatches out and places itself in intimate contact with the 

 embryonic plant tissue. This is followed in the galls found on 

 the hackberry, by an upward growth of the tissue about the 

 larva. The tissue above the larva never completely grows 

 together, leaving what is called in the present paper an ' ' apical 

 canal. " This very common type of gall is called by Kiister the 

 " umwallungen " form, a word very satisfactorily expressing 

 the real nature of the gall. This type of cecidium stands in 

 marked contrast to that in which the larva sinks into a diverti- 

 culum or pouch, a kind found on the leaf blade only. 



Of the nine galls set forth in this paper, only three have had 

 the adult insects associated with them described and named. 

 Patton (26) in order to illustrate a method of naming galls, 

 gave specific names to a few of the following galls, which Riley 

 (28) had described, but properly left unnamed. Riley did not 

 have the adult insects and Patton did not see Riley's galls, 

 so we have the interesting case of a gall insect being named 

 without the writer having seen either the gall or the insect. 

 These names of Patton's are omitted from the present paper. 



The galls described for the first time in this paper, are given 

 a list number, which can be referred to by the entomologist 

 who finally describes the adult insect. The heretofore unde- 

 scribed galls and those yet unnamed are placed provisionally 

 under the old genus name Cecidomyia, which has long served 

 as a "storage" place for itonid "insect^e imperfectas". 



All of the galls are not worked out to the same degree of 

 detail since they are of fundamentally different structure. 

 Two of the simpler forms, exhibiting contrasting specific 

 characters, have been chosen to adequately present, by full 

 treatment, the histology of the itonid types on the hackberry. 



