Classification of Galls. xxxiii 



Galls may be arranged in groups of gradually 

 increasing complexity, beginning with those like Spathc- 

 gaster haccaruin, and leading up to the complicated 

 structure of CyrJps Kollari. Beyerinck's classification 

 following that of Lacaze-Duthiers, is into five groups : — 



1. Simple galls, consisting of nutritive tissue enclosed 



in thin-walled parenchyma with vascular bundles : 

 Netirotcriis ostreits, Spathegaster albipes, S. 

 baccarum, S. Aprilinus. 



2. Galls similar to these, but having the nutritive tissue 



first enclosed in sclerenchyma, which forms an 



^ inner gall ' : 



Neuroterus lenticularis, N. laevittscuhis, N. 

 numismatis, N.ftmipennis, Aphilotrix Sieboldi, 

 A. autumnalis, A. radicis, A. globuli, Andricus 

 curvator, Biorhiza remim, B, aptcra. 



3. Galls possessing an inner gall like the last, but 



having it surrounded by thick-walled parenchyma : 

 Dryophanta longiventris, D. divisa. 



4. Galls with the inner gall enclosed in a spongy layer 



of branched parenchyma, with wide intercellular 

 spaces, and having the surface covered with 

 a differentiated epidermis : 



Unilocular. Dryophanta scutetlaris. 



Multilocular. Tei'as terminalis. 



5. Galls which have the inner gall enclosed in thick- 



walled parenchyma, and then in spongy tissue ; 

 and which have a differentiated epidermis : 

 Cynips Koltari. 

 Besides these histological differences, the outward 

 characters are also of varying complexity ; each infini- 

 tesimal improvement, which has been of service as 

 a protection against parasites, or has been successful in 

 securing natural conditions favourable to the life and 



