28 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



III. 



ON THE ORIGIN OF THE FORMS OF GALLS.. 



BY P. CAMERON, V.-P. 



[Read 23th Augnst, 1SS3.] 



The question of the origin of galls has occupied 

 the attention of observers of Nature from the 

 earliest times. It is unnecessary for me to 

 discuss the theories promulgated j)rior to the 

 apxDearance of the ^\^ork of Lacaze-Duthiers,"*" for 

 they have now only a historical interest. The 

 views of the eminent French Naturalist just men- 

 tioned have been generally accepted f in this 

 country as affording a satisfactory explanation of 

 the origin of galls ; but as they are, I believe, 

 erroneous and not in harmony with recent researches,. 

 I XDropose to state here my reasons for believing 

 them to be not in accordance with our knowledge 

 of the origin and growth of galls. 



Lacaze-Duthiers' theory was briefly this : His own 

 admirable researches into the morphology of the 

 ovipositor of insects had shown him that gall-flies 

 had, in connection with their ovipositor, a gland, 

 which, in the bees and wasps (which belong to the 

 same order as the gall-flies), undoubtedly secreted a 

 liquid of a x^oisonous nature. He therefore argued 

 that galls owed their origin to the liquid which was 

 deposited by the flies in the tissue of the plant 

 along with the eggs. To account for flies scarcely 

 distinguishable from one another, producing quite 

 dissimilar galls, it was further assumed that the 

 poison varied in its chemical and molecular con- 

 stitution in each species. Each species, in fact, had, 



*Annal. cles Sc. Nat. Bot. (3) xix. p. 273, et seq. 

 tSee Darwin, Animals and Plants under Doniest., ii. p. 273;, 

 Lubbock, Nature, vii. p. 448, 



