18 THEORIES OF GALL ORIGIN. 



galls. He assumed that the plant had a vegetable 

 soul, this vegetable soul presiding at the origin of 

 galls, with their eggs, larvse, and imagos ; while it, 

 again, gave issue to fruits. Linne explained the 

 matter by asserting that the galls were formed by the 

 outflow of sap from the wounded parts. 



Malpighi (Opera Omnia, De Grallis, 1679) may be 

 said to be the first scientific observer of galls. 

 Indeed, considering the time in which he lived, his 

 descriptions and figures of galls are wonderfully accu- 

 rate — much more so than those of Reaumur. Malpighi 

 noticed a fly oviposit in the leaf. He observed that 

 a liquid exuded, and from this he concluded that the 

 galls were caused by a process of fermentation ; the 

 liquid inserted acting as a ferment on a supposed 

 "vitriolic acid " which existed in the plant. 



Reaumur (Memoirs, vol. iii) advocated a theory of 

 mechanical irritation by the ovipositor, the egg (for 

 Reaumur was aware that the egg increased in size 

 after being deposited in the plant) larva, and also to 

 a supposed increase of temperature in the egg. He* 

 compared the egg with its supposed higher tempera- 

 ture contrasted with the plant to a small furnace giving 

 heat to all the surrounding fibres, this heat assisting 

 in their growth. The French naturalist, in his exa- 

 mination of the ovipositor, found that it varied in form 

 in different species. This diversity of form would act 

 differently when inserted in the plant, and hence would 

 lead to differently shaped galls being formed. As re- 

 gards the structure and consistence of the galls, he 

 states that it was easy to account for them by each 

 species absorbing during its development different 

 juices. Thus spongy galls, like Andricus terminalis,. 

 absorbed juices which developed spongy structures ; 

 woody galls, which gave origin to hard and woody 

 formations, from woody structures. 



Lacaze-Duthiers (Annales des Sciences naturelles, 

 Botanique, xix, 31) advocates what may be called 



* Memoirs, iii, p. 504, 



