382 Transactions of the Canadian Institute. [vol. ix 



gall cavity and above it. These cells give a false appearance 

 of a protective zone. X20. 



Fig. 42. Eurosta solidaginis Fitch on the stem of Solidago canadensis L. 

 Transverse section, showing the proliferation of glandular tis- 

 sue and the general arrangement of the glands along the lines 

 of the fibro-vascular bundles. X25. 



Plate VII. 



Fig. 43. Andricus piger Bassett on the leaf of Quercus coccinea Muench. 

 At the lower part of the figure a thick nutritive layer is shown, 

 bordering the larval chamber; outside of this tissue is the pro- 

 tective zone from which a cone-shaped projection originates 

 that blocks the canal leading in from the outside. The epider- 

 mis lining this canal is shown continuous with the general epider- 

 mis of the gall. X25. 



Fig. 44. Andricus piger Bassett on the leaf of Q. coccinea Muench. Sec- 

 tion showing a nearly complete larval chamber. The other 

 parts correspond to those in the preceding figure. The epider- 

 mis lining the canal is not shown so well in this case, as the section 

 passes along the edge of the canal. X25. 



Fig. 45. Andricus petiolicola Bassett on the leaf of Q. alba L. Section 

 passing through the main canal. The epidermis of the gall is 

 shown passing into the trichome bearing lining of the gall. X25. 



Fig. 46. Andricus petiolicola Bassett on the leaf of Q. alba L. Section 

 passing through the termination of the main canal, showing a 

 number of trichomes and two larval chambers blocked by masses 

 of sclerenchyma. X45. 



Fig. 47. Andricus (undescribed) on the leaf of Quercus macrocarpa 

 Michx. Section passing through the edge of a canal and show- 

 ing the two masses of sclerenchyma almost united. X35. 



Fig. 48. Andricus imbricaria Ashmead on the stem of Q. coccinea 

 Muench. Section showing the numerous bands of cells radi- 

 ating out from the boundary of the protective sheath, the light 

 coloured layer in the figure. The darker coloured nutritive zone 

 bounds the protective layer and lines the gall cavity. X20. 



Plate VIII. 



Fig. 49. Dryophanta palustris O.S. on the leaf of Quercus coccinea Muench. 



Section of a very early stage in which the inner and outer 



galls are still in contact. The following points are shown, a 



canal passing from the outside into the larval chamber, the 



