358 



Transactions of the Canadian Institute 



[vol. IX 



In galls other than the Cynipidse, the only cytological phenomena 

 that presented unusual features were found in the orders Diptera and 

 Lepidoptera. An unusual type of cell division was observed in the cortex 

 and epidermis of Neolasioptera perfoliata Felt (Text Fig. 7) and in the 

 cortex of Gnorimoschema gallceasterella Kellicott and Stagmatophora 

 ceanothiella Cosens. This has been already referred to in the descriptive 

 part of the paper and only the main features will be noted here. The 

 mother cells produce from 2 to 5 daughter cells and these remain in 

 groups that are easily recognizable. The elongated nuclei are found in 

 contact with the septating walls but not exactly opposite each other. 

 In the Dipterous genus Neolasioptera this was the only form of cell 

 division that occurred in the gall, but in the Lepidopterous genera it 

 was found only in a limited area of the abnormal tissue. 



Fig. 6. — Nuclei from the nutritive layer of 

 Aulactdea nabUi Brodie. 



Fig. 7. — Cell division in the epidermis and cortex 

 of Neolasioptera perfoliata Felt. 



The Beginning of Gall Development. 



In some species of galls that originate from stems, veins or petioles, 

 the eggs of the producer are deposited within the tissues of the host in 

 or near the cambium zone. Adler and Kiistenmacher have detected 

 eggs actually placed in that region, and while my own observations in 

 the case of Cynips? constricta Stebbins were made on older develop- 

 mental stages, yet the nature and arrangement of the tissues were such 

 as would seem to preclude any other conclusion. The origin of this gall 

 from the vein is shown in Fig. 53. In leaf galls that are produced in the 

 blade as Rhodites lenticularis Bass. (Fig. 63), a cambium is differentiated 

 in the mesophyll into which, in this case, the egg is inserted. Two inde- 

 pendent observers, Beyerinck and Weidel, have demonstrated beyond a 

 doubt, however, that the egg is in some cases placed on the epidermis 

 of the host, and consequently there are at least two distinct methods of 

 ovipositing. 



