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the epidermal zone, another part to the protective zone and some to the 

 well-defined fibro-vascular bundles which radiate from the central body 

 to the outer part of the gall. These fibro-vascular bundles are in general 

 much better developed than in the galls of group A. The protective zone 

 is subject to considerable variation in the different species ; it is quite 

 prominent in A. inanis and practically absent in A. coelebs. The nutritive 

 zone, as in the first group, is prominent only when the gall is young. 



In group C the writer has studied A. nubilipennis and A. pnmns. 

 Tbis group may be readily divided into three sub-groups as indicated 

 above. The species of sub-group (a) because of the inner radiating and 

 spongy substance, appear to be intermediate between group B and the other 

 species of group C. The species of sub-group (b) are more succulent than 

 the species of sub-group (c). 



My studies of A. nubilipennis demonstrate a thick parenchyma zone of 

 large succulent cells and very small fibro-vascular bundles which were 

 most numerous near the surface of the gall. The protective zone consisted 

 of a few layers of thin-walled cells. The nutritive zone was prominent in 

 the young galls and persisted quite late. 



My studies of A. primus demonstrated a very thick parenchyma zone, 

 much firmer and drier than in A. nuMUpennis, and in which were very few 

 small, fibro-vascular bundles. The protective zone was entirely absent. 

 The nutritive zone well developed in the young galls. 



In general it will be noted that in this genus we have (1) the galls 

 originating and developing in the normal maimer which results in the 

 formation of the four zones; (2) the variation in the parenchyma and 

 protective zones, which enables the above division and sub-divisions; (3) 

 that group A may be considered the most highly developed and sub-group 

 c of group C the lowest. The significance of this line of development can- 

 not be determined until we know more about other genera of gall-makers 

 and their galls. However, a study of the known geographical distribution 

 of the species of this genus is interesting in connection with this study. 

 In group A, Ampliibolips confluens is very widely distributed over Canada, 

 the Eastern States south to Georgia, and west to Colorado, while the other 

 three species have much more limited ranges, two and possibly all 

 three within the range of the first. In group B we find that A. inanis 

 ranges from Canada and the Eastern States west to Iowa and south to 

 North Carolina ; A, cooM has almost the same range ; A. iUcifolice, A, 



