352 Transactions of the Canadian Institute [vol. ix 



The surface of the gall is smooth or covered with short weak spines. 

 Colour green, tinted strongly with red. 



Dimensions: — Diameter 5-6 mm. 



This gall resembles closely the preceding species in anatomical 

 structure. The cells of the nutritive and parenchyma layers differ in 

 much the same way and to the same extent. Further, the protective 

 zone is again absent. The explanation given in the two preceding forms, 

 to account for the scale in the depression at the summit of the galls, is 

 applicable also in this case. 



Cynips? constricta (Stebbins). 

 Host Quercus coccinea Muench. 



A monothalamous gall originating from the midrib or a principal 

 vein of the leaf. Its origin from a vein is shown in Fig. 53. It is usually 

 found on the under side of the leaf but occurs occasionally on the upper 

 side. 



This gall has the form of a sphere surmounted by a short cylindrical 

 neck, which is slightly constricted at the base. The general form is 

 shown in Fig. 54. A very small portion of its surface attaches it to the 

 leaf. The epidermis on the main body of the gall is smooth, shiny and 

 green in colour. The neck is red at the tip. 



Dimensions: — Diameter of spherical part 2.5-3.5 mm. 



At an immature stage of the gall the parenchyma zone in the 

 spherical part consists of a mass of cells that gradually decrease in size 

 from the epidermis to the inner limit of the layer. At the epidermis 

 the cells are nearly circular in outline but become square or rectangular 

 in proportion to their proximity to the centre. 



Bounding this zone on the inside is a crystal layer of about three 

 cells in thickness, each cell containing a large crystal mass. Around the 

 inside of this tissue is a nutritive zone, the cells of which are regularly 

 rectangular. 



At the top of the main part of the gall is a well-defined cambium 

 tissue which produces the cylindrical projection that caps the spherical 

 portion (Fig. 54). The anatomical structure of this part shows clearly 

 that it functions as an outer nutritive zone. Its walls are thin and the 

 cell contents take the same stain as those in the nutritive zone surround- 

 ing the larva. Large starch grains are also scattered throughout the 

 cells. This zone is separated from the cambium tissue in the later de- 

 velopmental stages by a protective layer of typical porous sclerenchyma. 

 These cells are filled with protoplasmic material, and the system of canals 

 between the individual cells is very complete and clearly defined. This 

 feature is very important since the nourishment from the outlying nutri- 

 tive zone has to pass through this tissue to reach the larva. 



