428, , The Ohio Naturalist [Vol. Ill, No. 7, 



between the protective and parerichyina zones, thus leaving the 

 two inner zones as a small sphere rolling free within the larger 

 sphere which is formed by the two outer zones. 



In Diastrop/iKS siiinnis Basset (Figs. 66, a, b; 67; 68, a, b, c, d; 

 69) we have a Cynipidous.gall occurring on Nepeta glechoma. I 

 secured a very complete series of this gall and made a very careful 

 stud)' of its development. In the youngest gall (Fig. 66, a, b) 

 we have the cell character of the leaf transformed into a mass of 

 small, irregular cells which can be readily divided into two zones, 

 the outer of which has the larger cells. At this time the cells are 

 very compact, but as the gall grows older intercellular spaces are 

 developed, the entire structure becomes loose and spongy and the 

 cells become larger. 



As the galls grow older a well-defined zone of flattened cells 

 is developed in the parenchyma near the epidermis, and fibro-vas- 

 cular bundles ( f . v. b. ) are developed at right angles to the sur- 

 face (Fig. 67). Up to this time the cells are small, irregular and 

 compact. The epidermis (ep) and parenchyma ( pa) zones are 

 well defined, but the distinctiion between protective and nutritive 

 zones cannot be made. 



As the gall grows older a cleavage plane is formed in the paren- 

 chyma just inside the zone of flattened cells (Fig. 68, a). A 

 careful examination of the parts thus cut off and surrounding the 

 larval chamber (1. c. ) shows two well-defined zones which corre- 

 spond to the nutritive and protective zones described in Part I. 

 At this time there is no marked difference in the amount of food 

 suppl}^ of the two zones. In the outer part formed by this cleav- 

 age plane we have the parenchyma (pa) and epidermal (ep) 

 zones (Fig. 68 c). Connecting the parenchyma and protective 

 zones we find ribro- vascular bundles (f . v. b. ) surrounded by par- 

 enchyma cells (Fig. 68, d). The character of these connecting 

 strands is ver}- similar to that described for H. centricola (Part I, 

 Fig. 27) and A. inanis (Part I, P'ig. 28), but contains more par- 

 enchyma tissue than either. However, the parenchyma cells are 

 not so elongated as in C. papillatus (Part I, Fig. 30). As the 

 gall grows older the cells of the protective zone become clear and 

 the cell walls of the nutritive zone gradually thicken (Fig. 69), 

 many undergoing complete degeneration, while others assume the 

 character of the sclerenchyma. 



CONCIvUSIONS. 



1 . All conclusions given in Part I are emphasized by the study 

 of the development of the galls. 



2. In the formation of all leaf galls except the Cecidomyia 

 galls, the normal cell structure of the leaf is first modified by the 

 formation of a large number of small, compact, irregular-shaped 

 cells. In the galls of Acarina and Aphididae this is followed by 



