i893. ETIOLOGY OF VEGETAL GALLS. 355 



member of our British Cynipidae. It is said to be indigenous to 

 France, and to resemble very closely the Aleppo gall, or galls of 

 Commerce [Galla tmctovia of Olivier). 3 



It first appeared in this country, or was first noticed here, some 

 50 or 60 years ago, and was then limited to Devonshire and other 

 of the South Western Counties. Gradually it extended itself inland, 

 and is now, I believe, to be found abundantly in nearly all parts of 

 Great Britain. It is the only one of the group to which the ink-gall 

 belongs that occurs so far North as England or even Northern 

 Germany .-^ 



Each gall, with regard to position, occupies the place of a 

 terminal or axillary bud, fiom the side or growing point of which 

 it is developed ; but I have occasionally met with instances in which one 

 gall has grown out of or been superimposed upon another during its 

 development. In its early condition, the gall is more or less cone- 

 shaped, with pointed apex, and is slightly pubescent. It is then of a 

 bright green colour, the surface spotted thickly over with crimson. As 

 development proceeds, the crimson spots, which assume a scale-like ~ 

 aspect, separate wider and wider from each other ; and the pointed 

 apex, though persisting for a time, and in some instances altogether, 

 usually disappears, leaving the gall at maturity more or less spherical 

 in form, and lightish brown in colour. 



In ordinary seasons, the young galls are first met with in July, 

 and mature in August or September. This year, owing to the 

 exceptionally bright weather of the spring, I found them as early 

 as the 2oth of June, and even at that date they had attained a diameter 

 of from half to three-quarters of an inch. 



The ovum of the gall-producing insect is, in this case, deposited 

 in or near to the young bud of the oak at an early stage of its develop- 

 ment, before any part of the cellular tissue is differentiated into leaves 

 or other special organs ; except, it may be, the few embryonic scales 

 by which it is at times surrounded. 



What is there, we may ask, in the casual presence of the little 

 ovum ; in the action of the developing larva ; in the mechanical 

 puncture of the parent cynips ; or in the deposit of a tiny drop of 

 irritating fluid by which it is said the ovipositing is accompanied ; 

 what is there, I ask, in any one, or more, or all of these, or, it may 

 be, in the action of some other factor yet to be discovered, that impels 

 those wonder-working changes by which the gall itself is produced, and 

 by which its future growth and development are accompanied ? What 

 is it that, in the presence of this new agent, leads the succulent cells 

 to resign their normal tendencies, and, instead of differentiating into 



=* The Gall-producer is Diplolepis or Cynips galla: tinctorij:. — " The gall of Cynips 

 tinctovi^," says Dr. G. L. Mayr, " occurs in the southern half of Europe, and near 

 Vienna is frequently met with ; that of C. kollari, however, is found as far as the 

 German Ocean." — 7 Entomol., 242. 



* Zool. 4964, sec. 7, Entom., 245. 



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