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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. prunus. 
This 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 (¢). 
My studies of A. niubilipennis 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. prunus demonstrated a very thick parenchyma zone, 
inuch firmer and drier than in A. nubilipennis, 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 manner 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 
ce 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. Iowever, a study of the known geographical distribution 
of the species of this genus is“interesting in connection with this study. 
In group A, Amphibolips 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, cooki has almost the same range; A. ilicifolie, A, 
