348 Transactions of the Canadian Institute [vol. ix 



larval cells towards which the canals are passing. The cells of this tissue 

 are identical with those of the ordinary protective zones. 



From analogy with Dryophanta palustris O.S. (Fig. 49), and with 

 other species of Andricus it would seem safe to infer that this canal opens 

 into the larval chamber at earlier stages in the development of this gall. 

 This also appears more likely to be the case since the protective zone 

 that blocks the way, is differentiated only in the later stages. 

 Andricus petiolicola Bassett. 

 Host Quercus alba L. 



This gall is produced in the same manner as A. piger Bassett by the 

 swelling of the petiole or midrib. It is also located at the same place on 

 the leaf as that species. 



It has an irregular, spherical shape drawn out at some place on its 

 surface into a short tapering projection. At the summit of this elongated 

 part of the gall is an opening surrounded by a dense ring of coarse, brown 

 trichomes. The larval cells are numerous and very variable in number. 

 They are arranged around the axis of the gall at about the same distance 

 from the epidermis. 



Dimensions: — Diameter of the swollen basal part 10-12 mm. 



In this species the protective layer is much thicker than in A. piger 

 Bassett, but the individual cells composing it are the same in both species. 

 The galls sectioned were nearly mature but the crystal layer of the former 

 species was not found. 



In this species also there is a canal passing towards each larval 

 chamber (Fig. 46). These canals do not open directly to the outside 

 but into a main canal of larger bore that extends a considerable distance 

 into the mass of the gall (Figs. 45, 46). The branch canals are blocked 

 by the protective sheath as in the preceding species. All of the canals 

 are lined with a cuticularized epidermis, continuous with the gall epi- 

 dermis (Fig. 45). The lining of the main canal produces abundant tri- 

 chomes but these structures do not appear to be present in the tribu- 

 taries. A tubular outgrowth of the protective zone surrounds the main 

 canal. This sclerenchymatous sheath is separated from the canal by 

 several layers of parenchyma cells. Outside of this protective tube a 

 cork cambium is differentiated. 



Andricus (Undescribed) . 

 Host Quercus macrocarpa Michx. 



The swelling of the midrib of the leaf produces this gall. It resembles 

 closely A. piger Bassett, but is always found within the blade of the leaf, 

 although close to its base in most cases. 



The openings mentioned in the two preceding species are in this 

 case found on the surface of the gall which appears on the upper side of 



