1893. ETIOLOGY OF VEGETAL GALLS. 361 



scales, so as completely to separate the cone-like apex with its 

 appendages. In the space thus prepared (for the severed cone is still 

 retained in situ by the enclosing scales), a variable number of eggs is 

 deposited ; sometimes, it may be, but a dozen or two ; at others, as 

 many as 200 to 270 or more. It is not altogether without wonder 

 that one reahses the possibility of a lodgment being found for so 

 many eggs in so small a space, a space not one-fifth of an inch in 

 transverse diameter across the bud, and less than one-fiftieth of an 

 inch in depth. ^^ 



Each egg consists of a white, semi-transparent, pyriform body, 

 with a long, silvery filament or pedicel at its smaller end. To the 

 base of the detached cone, the distal ends of the several egg-pedicels 

 are, as a rule, anchored, so as to leave the ova pendent, with their 

 broad ends downwards, towards the fixed surface of the cut axis. 



As winter passes away, and slumbering vegetation begins to feel 

 the stir of new activities, a further phase in the life-history of the gall 

 and the gall-insect commences. Fed by streams of nutritive sap 

 which now circulate through the tree, the young, uninjured buds 

 begin to swell, and the green axes to elongate. 



With those, however, which have been severed by the cynips, 

 another and a different result takes place. Should ova, notwith- 

 standing the incision, fail to be deposited, or, if laid, perish during 

 the winter, no growth, normal or abnormal, takes place from the 

 divided axis. This remains brown, dry, and inactive. But if, on 

 the other hand, healthy ova are present, and these, in due course, 

 hatch out their living embryos, then, by the action of these upon 

 the dormant tissues, new and peculiar powers of growth are 

 manifested in the cut axis — powers which result in the production, 

 not of a normal branch, but of an abnormal, tumour-like gall. 



Cognate facts with regard to the galls of Cecidomya vevbasci, found 

 on the stamens of the Figwort and hoary Mullein {Scrophnlaria canina 

 and Veyhascumpulvernlentum), have been noted by M. Leon Dufour.^7 



" From meteorological influences or other little-understood cause, 

 it happens at times, he says, that the larva of this insect dies soon 

 after leaving the egg. Then the parts in course of enlargement tend 

 to recover ; the fundamental excitement, which would be continued 

 by the suction of the embryo, stops and fades ; the swollen tissues 

 (subjected again to normal physiological laws) contract and shrivel ; 

 the sap loses its morbid exuberance, resumes its normal course, and 

 at last, though slowly, the stamens re-enter upon their generative 

 functions, while the lobes of the corolla spread out and display them- 

 selves, and, in the end, recover their bright and glowing colour. Under 

 other circumstances, where the death of the larva thus ensues — the 



!•' In the ovaries of B/o;7(/>(i aptcra, v^hxch gives rise io Teras termimilis, I have 

 found 1,326 ova — in one instance as many as 1,570 — the whole length of the abdo- 

 men being less than one-eighth of an inch, that of Tcras terminalis only half as much. 



1' Ann. des Set. Nat., vol. 1., 1846. 



