May, 1916] Morphology of the Zoocecidia of Celtis 289 



Plate XV. 



. Fig. 6. Gall of Pachypsylla mamma (mature). X 4. 

 Fig. 6a. Vertical median section through mature gall. X 4. 



Fig. 6b. Diagram of a slightly immature specimen. Median, vertical section. X 36. 

 Fig. 6c. Detail of part c, Fig. 6b. X 85. 

 Fig. 6d. Detail of part d, Fig. 6b. X 85. 

 Fig. 6e. Detail of part near e, Fig. 6b. X 85. 

 Fig. 6f. Normal leaf cystolith at f, Fig. 6b. X 340. 

 Fig. 6g. Aborted cystolith at g, Fig. 6b. X 340. 

 Fig. 6h. Detail study of nutritive tissue close to blind end of apical canal, showing 



criss-cross thickening of cell walls. X 125. 

 Fig. 6i. Parenchyma and scleride cells from mature gall. X 85. 

 Fig. 6k. Parenchyma from leaf mesophyll. X 85. 

 Fig. 6m. Parenchyma from petiole cortex before thickening. X 85. 

 Fig. 6n. Parenchyma from twig pith. X 85. 



Plate XVI. 



Fig. 7. Gall of Pachypsylla venusta. X 1J^2- 



Fig. 7a. Longitudinal median section of P. venusta. X IJ^. 



Fig. 7b. Tangential section of gall, showing flocculent waxy material developed 



by the nymphs of P. venusta. X IJ^. 

 Fig. 7c. Transverse section of gall. X lYi- 



Fig. 7d. Detail of outer part of wall indicated at d, in enlargement near 7c. X 100. 

 Fig. 7e. Detail of inner part of wall indicated at e near Fig. 7c. X 100. 

 Fig. 7f. Lignified cell with simple pits illustrating the type of cell comprising the 



core of the gall. X 400. 

 Fig. 7g. Multicellular trichomes lining the canals leading into the chambers. See 



g, Fig. 7a. X 100. 

 . Fig. D. Cross section of normal petiole. X 170. 



Plate XVII. 



Fig. 8. Gall of Cecidomyia unguicola. X 6.25. 



Fig. 8a. Detail study of longitudinal, median section of gall. X 36. 



Fig. 8b. Detail study of a transverse section of gall taken distal from the gall 

 base, about one-third the length of the gall. X 36. 



Fig. 8c. Trichomes found in the apical canal. X 170. 



Fig. 8d. Sclerenchyma and crystal-bearing cells found at proximal end of pro- 

 tective layer. X 340. 



Fig. 8e. Sclerides of one year old stem adjoining bast fibres. X 340. 



Fig. 8f . Sclerides of three year stem with associated crystal-bearing cells. X 340. 



Fig. 9c. Sclerenchyma cells and crystal-bearing cells from proximal side pro- 

 tective layer of Phytophaga celtiphyllia (9a). X 340. 



Figs. 10-lOa. Phytophaga wellsi. Gall and vertical median section of gall. X 4.1. 



Figs. 11-lla. Cecidomyia sp. Gall and median section of gall. X 6.25. 



Figs. 12-12a. Cecidomyia sp. Gall and median section of gall. X 4.1. 



Figs. 13-13a. Cecidomyia sp. Gall and median section of gall. X 6.25. 



Fig. 13b. Details of distal end of median section of gall 13. X 85. 



Figs. 15-15a. Cecidomyia sp. Gall and median longitudinal section of gall. X 4.1. 



Fig. 15b. Transverse section of gall 15. X 6.25. 



Pl.\te XVIII. 



Fig. 9. Gall of Phytophaga celtiphyllia. X 6.25. 



Fig. 9a. Vertical median section of gall of Phvtophaga celtiphyllia .shown in 



detail. X 36. 

 Fig. 9b. Details of cells found in region near b in Fig. 9a. X 140. 

 Figs. 14-14a. Cecidomyia sp. Gall and median section of gall. X 4.1. 

 Figs. 16-16a. Cecidomyia sp. Gall and median section of gall. X 6.25. 



