ii8 The Ohio Naturalist. [Vol. IV, No. 6, 



ripes (Figs. lo, 43), and P. acericola (Figs. 11, 45). These con- 

 volutions result in the formation of a more or less well defined 

 cavity, and trichomes are developed in great abundance in the 

 younger stages ; (3) Thickening of the parts which become cov- 

 ered with an abundant growth of trichomes as in the case of E. 

 anomalum (Figs. 47, 48). 



The Phytoptus galls show two fairly well-defined zones, the 

 outer made up of rather large cells and the inner of much smaller 

 cells, which are very rich in protoplasm and which supply nour- 

 ishment for the young animal (Fig. 77). As the galls approach 

 maturity the protoplasm disappears, first from the outermost cells 

 and lastl}^ from the cells on the inner surface. As the protoplasm 

 disappears the tannin accumulates in great abundance (Fig. 78). 



2. GALLS OF THE APHIDIDAE. 



Man}' of the Aphididae galls produce trichomes which soon 

 disappear. At first all the cells contain protoplasm and divide 

 rapid!}', but as the galls approach maturity the tannin increases 

 in abundance. 



Schizoneura americana Riley (Fig. 12), Colopha ulmicola Fitch 

 (Fig. 13), and Hormaphis hamamelis Fitch (Fig. 15) have been 

 considered in Part I. 



In Pemphigus populi-transversus (Figs. 55, 56) and P. p.-caulis 

 (Figs. 57, 58) the thickness of the walls of the galls is much 

 greater than an}- other members of this family and the cells are 

 more uniform in character. These galls are especially well sup- 

 plied with fibro-vasular bundles and are very dense. 



In P. vagabundus (Fig. 112) we have a gall in which many of 

 the cells are elongated similar to C. ulmicola and H. hamamelis. 

 Its close structural resemblance to C. ulmicola and H. hamamelis 

 and unlikeness to P. p.-transversus and P. p.-caulis is due to the 

 fact that P. vagabundus, C. ulmicola, and H. hamamelis are 

 formed on the blades of the leaves, while P. p.-transversus and 

 P. p.-caulis are formed on the petioles which are made up largely 

 of fibro-vascular tissue. My specimens of these galls were mature, 

 and I am therefore unable to say anything concerning their early 

 stages. 



In the Phylloxera galls all tl e cells are at first rich in pro- 

 toplasm and the tannin does not form in abundance until very 

 late. The two zones are fairly prominent. In P. c.-caulus Fitch 

 on H. ovata, a gall which forms on both blade and petiole of the 

 leaf and also on young stems large intercellular .spaces are formed 

 near the surface. 



3. (iALL.S 01* PSVLLIDAE. 



Pachypsylla c. -mamma Riley has been described in Part V 

 (Figs. 59, 60). 



