344 Transactions of the Canadian Institute [vol. ix 



cavity a typical nutritive layer has been formed by the elongation of the 

 cells in a radial direction. In the centre zone the lines of cells containing 

 the vessels are much more apparent at this stage, since the intervening 

 tissue has become loose and skeleton-like. The cells composing it are 

 long, very narrow and frequently branched. In many cases a branch is 

 attached to the main cell without the formation of an intersecting par- 

 tition between the two. The outside zone of the three is composed of 

 somewhat elliptical cells. These form a fairly firm tissue constituting 

 the rind of the gall. 



(c) Mature stage. 



The protective zone is now the most characteristic feature of the 

 anatomical structure. The part of the protective sheath adjoining the 

 larval cavity consists of a few layers of elliptical cells arranged in tan- 

 gential rows. The sclerenchymatous deposits on the outside walls of 

 these cells are much heavier than those on the inside. Further out the 

 protective cells are formed in radial rows and their walls are uniformly 

 thickened. This protective strengthening of the cell walls extends even 

 into the loosely arranged filament-like cells, some of which are heavily 

 sclerified. 



Amphibolips inanis O.S. 

 Hosts Quercus coccinea Muench. 

 Quercus rubra L. 



Resembles the preceding species in external appearance and in its 

 attachment to the midrib or the petiole of the leaf. 



In shape it is more nearly spherical than A. confluens Harr. and it 

 has a much thinner rind than is found in that species. The epidermis 

 of the gall, which is at first green with dark spots, becomes light brown 

 with darker patches at a later stage. The larval cell in this case is held 

 in position by a number of fine radiating fibres. 



Dimensions: — Average diameter 35 mm. 



In the earlier stages the anatomical structure of this gall is practi- 

 cally the same as A. confluens Harr. The vascular strands surrounded 

 by elongated cells are present, but as the gall becomes older the connect- 

 ing tissue from between the strands disappears. 



In the mature gall the protective zone is very apparent. It consists 

 of 8 to ID rows of comparatively small elliptical cells. The walls of these 

 cells are uniformly thickened, constituting a porous sclerenchyma. 

 Dryophanta palustris O.S. 

 TT . (Quercus rubra L. 



\Quercus coccinea Muench. 



A monothalamous gall produced singly or in groups of two or more 

 on the leaves of the host plant. It is spherical in form and extends almost 



