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The Ohio Naturalist. 
[Vol. Ill, No. 7 , 
between the protective and parenchyma 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 Diastrophus siminis Basset (Figs. 66, a, b; 67; 68, a, b, c, d; 
69) we have a Gynipidous gall occurring on Nepeta gleclioma. I 
secured a very complete series of this gall and made a very careful 
study 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 
supply 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 fibro-vascular bundles (f. v. b.) surrounded by par- 
enchyma cells (Fig. 68, d). The character of these connecting 
strands is very 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. 
CONCLUSIONS. 
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 Ceeidomyia 
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 
