MODIFICATIONS OF GALL-GROWTH. 



131 



and the most easily-recognised abnormal forms of Kollari 

 galls are the half-sized, irregularly shaped, and slightly 

 discoloured specimens which are so commonly met with, 

 and which invariably lose their green colour {i.e. become 

 ripe) later than normal specimens. In section these will 

 show the larva chamber to be greatly enlarged and the whole 

 structure altered : the parenchymatous tissue is hardened, 

 and the surroundings of the central cavity is thick and hard; 

 in fact the whole cellular tissue is condensed. This central 

 cavity is filled with numerous chambers separated by thin 

 septa, as before instanced in other cases of synergous 

 tenancy : in these the Synergiis larvae reside. They are 

 vegetable feeders, consequently the sap (plant juices) is 

 appropriated by them, and the gall becomes dwarfed, and its 

 tissues improperly nourished. Various forms of this modifi- 

 cation occur, but it is unnecessary to particularise them : a 

 section of one is shown in the accompanying figure (see fig. c). 



Fisr. A. 



Fiff. B. 



Fig. C. 



Particularly small, thin-walled, woody, slightly pointed, 

 conical galls are frequently met with amongst those of 

 C. Kollari. These are, I believe, 

 galls of that species modified by a 

 species of Synergus : one egg is 

 laid in the immature cell oi Kollari, 

 and, as before, the sap is appro- 

 priated by the tenant, but to a 

 greater degree than in the former 

 many-chambered instance. It is 

 necessary to say that the history 

 of the production of this form from 

 Kollari is only surmise; its actual 

 proof is difficult. 



The production of Rhodites eglanterice is a thin-walled, 

 globular, glabrous, green or rosy gall, occurring normally on 

 the under side of the common wild rose {Rosa spp.) : for 

 section see fig. «. As an instance of the gall being unaltered, 



Small C. KoUiiri galls. 



