a Note on the early stages of its development. 17 



and the two soon meet. When this happens any further growth 

 goes on chiefly on the dorsal side, and the leaf becomes asym- 

 metrical in transverse section. The outer (dorsal) side of the 

 needles soon comes in contact with the inner surface of the bud- 

 scales, but as these are gradually unfolding all the time, they do 

 not offer much resistance to the swelling, and the dorsal side of 

 each gall needle consequently becomes convex in shape. 



Owing to the erect position of the needles at this stage and 

 their crowded spiral arrangement round the main axis, this 

 enlargement of their bases quickly results in adjacent needles 

 coming into contact with each other, and grooves are formed on 

 the surface of each needle, where other needles have pressed upon 

 it. The phyllotaxis is such that the base of any one needle must 

 on swelling come in contact with the swollen bases of no less than 

 four other needles, two belonging to the spiral above it, two to the 

 spiral below. 



Each needle-base is consequently marked with four grooves. 

 Of these, the two on the inner side are much deeper than the 

 two on the outer side, owing to the pressure being greater in 

 the former case, and between these grooves a slight ridge is 

 formed which corresponds with the space between the needles 

 of the spiral above, or below as the case may be. 



As the stem gradually elongates the needles are carried slightly 

 apart, and the resulting space above each needle forms a chamber 

 which is later on taken possession of by the young offspring of the 

 Chermes mother. The deeply grooved inner (ventral) side of the 

 needle forms the floor of this chamber, whilst the two needles of 

 the spiral above each contribute a half towards the formation 

 of the roof. It will thus be seen that each individual leaf 

 participates in the formation of three distinct chambers, its 

 ventral side forming the floor of the chamber above it, and the 

 grooves on its dorsal side each forming one-half of the roofs of 

 the two chambers below it to right and left. 



At a later stage these chambers become closed in by the 

 development of thick tumid lips around their mouths. 



About the beginning of May the shoots begin to emerge from 

 the bud-scales but the galls are not at once visible since the 

 base of the shoot is still concealed in the persistent basal bud- 

 scales. They soon however make their appearance and the galls 

 then enter on the second stage of their existence, the history 

 of which must be left at present as my examination is not yet 

 completed. 



But to return to the insect. Whilst the changes described 

 above have been proceeding in the bud, the Chermes larva has 

 been steadily sucking and increasing in size. She has secreted 

 a quantity of white wool-like wax, which, while it entirely conceals 



vol. xm. pt. i. 2 



