342 Transactions of the Canadian Institute [vol. ix 



In the earliest stage examined the gall was 2 mm. in diameter. 

 At this time none of the cell walls are sclerenchymatous and the nutri- 

 tive zone is only about four narrow cells in width. Outside of this layer 

 is a part of the parenchyma zone in which each cell contains a large 

 crystal mass. 



At a stage in which the gall is full grown but still soft, all the zones 

 are differentiated. The epidermis is thrown into folds and is covered 

 with a heavy cuticle (Fig. 64). This is absent in the sinuses of the folds 

 and on the epidermis covering the spines. The parenchyma zone is 

 gradually converted into a protective tissue of porous sclerenchyma. 

 The thicker deposit is usually on the walls of the cells nearer the periphery 

 of the gall. Along the outside of the nutritive zone and throughout the 

 protective layer generally are lines of small cells almost square in outline. 

 The walls of these cells are very thick and the lumen of each is filled with 

 a single crystal or a mass of crystals. In galls that had become hard all 

 the cells of the parenchyma zone were found to have sclerified. The 

 sclerification is partially complete in Fig. 64. 



The nutritive layer of this gall differs very little in appearance from 

 the parenchyma zone. Its cells do not contain the rich protoplasmic 

 contents common to the nutritive zones of typical Cynipid galls. 



Philonix hirta Bassett. 

 Host Quercus macrocarpa Michx. 



A monothalamous, spherical gall originating from a principal vein 

 of the leaf. Found somewhat irregularly spaced along the vein and about 

 equally distributed between the upper and lower surfaces of the leaves. 



The epidermis has the same faceted appearance found in the pre- 

 ceding species, but in this form the trichomes are represented only by 

 short points. Colour greenish yellow. When the leaves become tinted in 

 the autumn the galls assume a reddish brown colour. 



Dimensions: — Diameter 2-3 mm. 



The anatomical structure of this gall differs from P. erinacei Beut. 

 only in the distribution and nature of the protective zone. This tissue 

 is limited to a layer 3 to 4 cells in thickness, just outside the nutritive 

 zone. The sclerifying deposits are limited almost entirely to the outside 

 tangential walls of these cells and gradually entirely fill them. As a 

 result of this the pores pass completely across the cells in the older 

 stages. The small square crystal-bearing cells are, in this species, just 

 outside the regular protective sheath. 



Philonix nigra Gillette. 

 Host Quercus alba L. 



A monothalamous gall attached to the principal veins on the under 

 side of the leaf. 



