1912] Morphology and Biology of Insect Galls 383 



trichome bearing epidermis of the gall continuous with the 

 lining of this canal and passing into the inner row of cells of 

 the nutritive zone, the bay-like depression in this zone where 

 the canal enters. X30. 



Fig. 50. Dryophanta palustris O.S, on the leaf of Q. coccinea Muench. 

 Section of a somewhat more mature stage than the preceding, 

 showing the commencement of the separation of the inner gall 

 from the outer in the region of the cambium layer. X 12. 



Fig. 51. Dryophanta palustris O.S. on the leaf of Q. coccinea Muench. 

 Section of the wall of the inner gall, showing the nutritive zone 

 with a line of collapsed cells next the larval chamber and a row 

 of empty cells just inside the collapsed tissue. The protective 

 layer borders the nutritive on the outside and a few round cells 

 of the parenchyma adhere to the protective zone. X70. 



Fig. 52. Dryophanta palustris O.S. on the leaf of Q. coccinea Muench. 

 Section of the larval chamber of a mature specimen, showing 

 the insect breaking out of the inner gall. At this stage the 

 nutritive layer has entirely collapsed. X15. 



Fig- 53- Cynips ? constricta Stebbins on the leaf of Q. coccinea Muench. 

 Longitudinal section showing the origin of the gall from the 

 midrib of the host in the region of the cambium layer. Xioo. 



Fig. 54. Cynips ? constricta Stebbins on the leaf of Quercus coccinea 

 Muench. Longitudinal section of an early developmental 

 stage showing the general structure of the gall. The dark mass 

 at the top of the figure represents the supplemental nutritive 

 zone of the gall ; it is separated from the spherical part of the 

 gall by a cambium tissue. The protective sheath that separates 

 the nutritive from the cambium in later stages is not yet dif- 

 ferentiated. A nutritive zone is also shown lining the larval 

 chamber. X40. 



Plate IX. 



Fig. 55. Holcaspis bassetti Gillette on the stem of Quercus macocarpa 

 Michx. Section through the gall cavity with enclosed larva. 

 The character of the cells of the nutritive zone is shown and the 

 unbroken edge of its inside boundary. The finely divided 

 material of the stomach contents of the larva is also shown. X60. 



Fig. 56. Section of a larval inquiline from the gall Holcaspis bassetti 

 Gillette. The broken edge of the tissue on which the larva 

 has been feeding is shown, also the comparatively coarse material 

 of the stomach contents. X60. 



