The Ohio ^A(^atiiraUst, 



PUBLISHED BY 



The Biological Club of the Ohio State Uni'versity, 



Volume II. MAY. 1902. No. 7. 



GALLS AND INSECTS PRODUCING THEM. 



Melville Thurston Cook. 



Part i. The Morphology of IvEaf Galls. 



The purpose of this study was to contribute to the knowledge 

 of cellular activity of the plant under peculiar animal stimulus ; 

 to compare the effects of the two sets of insect organs, mouth 

 parts and ovipositors, and to throw additional light on the classi- 

 fication. The statements made in this paper are based on a large 

 number of collections. The collection of stem galls was too 

 incomplete to draw conclusions and is therefore reserved for a 

 future paper. No attempt was made to follow the development 

 of the galls but rather to make a comparison of the structure of 

 the various forms of galls. 



My paper was practically complete before I received the papers 

 of H. Fockeu. After receiving his paper I reviewed ni}' own to 

 determine wherein my results agreed with or varied from his 

 conclusions. Experiments such as are described by H. Fockeu 

 to ascertain the cause of the gall formation were not attempted. 



Fockeu' s studies were grouped according to the plants affected ; 

 my own studies werfe grouped with reference to the insect pro- 

 ducing the galls. 



methods. 



For the killing and fixing, several fluids were used, but the 

 most successful were Chromo-acetic and Picric-alcohol. A num- 

 ber of different stains were used, but Delafields-Haemotoxylon, 

 proved very satisfactory for most work. 



For the drawings a Bausch & Lomb microscope and camera 

 lucida were used ; for the normal leaf, a i-inch ocular and a 

 i-inch objective, and for the galls a i-inch ocular and a 23-inch 

 objective. Since it was unnecessary to make drawings of the 

 entire galls, drawings were made from one or more parts to show 

 the characteristic structure, and this part is indicated on the small 

 diagrammatic drawings. Since the galls were so variable in size, 

 it was practically impossible to make the diagrammatic drawings 

 on a definite scale. 



GENERAL CLASSIFICATION. 



As a matter of convenience the following temporary classifica- 

 tion, based on location of the galls was adopted for this and other 



