16 Mr Bur don, The Pine-apple Gall of the Spruce: 



felt at the periphery and it is here consequently that the most 

 abundant precipitation of starch takes place. 



The sweet drops of " Honeydew " which, as is well-known, are 

 exuded by these insects, may perhaps prove to have the closest 

 bearing on this point. 



In connection with this suggestion I must however state that 

 I have not yet succeeded in demonstrating the presence of glucose 

 in the gall, but hope to carry out some careful tests next spring 

 when the galls are again in season. 



I have mentioned above that the nuclei enlarge in about the 

 same proportion as the cells containing them, but the change is 

 not confined merely to enlargement. In the normal resting 

 nucleus the chromatin network is very evenly distributed, and 

 no well marked nucleoli are to be found. In microtome sections 

 one of the first indications that a cell is destined to form part of 

 the gall tissue is given by the chromatin of the nuclei. The 

 network gradually becomes fainter and fades away, while at the 

 same time numerous nucleoli make their appearance. In course 

 of time the network in some cases entirely disappears and the 

 whole of the chromatin becomes aggregated into these nucleoli. 

 Some of them attain a considerable size and project like warts 

 from the surface of the nucleus, which assumes a pallid unhealthy 

 appearance. 



So far as I have examined them at present, the mitotic figures 

 seem to be of the usual somatic type, and I have found no indica- 

 tion of heterotypical mitoses, such as one would expect to find 

 were the growth of a cancerous nature. 



The net result of these various changes is that almost all 

 previous differentiation of the stem has been obliterated, and in 

 its place a parenchymatous tissue, consisting of abnormally swollen 

 cells with extremely thin walls, has been formed. The cortex on 

 the galled side of the stem has become 2 to 3 times as thick 

 as the cortex on the other side which is still normal, and the 

 symmetry of the stem has thus been destroyed. 



The gall growth continues its outward course until it reaches 

 the bases of the needles, and these in their turn begin to swell up. 

 As the growth proceeds up them the needles assume a tapering 

 shape — ver} 7 much thickened at the base and gradually diminish- 

 ing in size until about half-way up, where they still remain normal. 

 The gall is now visible to the naked eye as soon as the bud-scales 

 are removed, being rendered evident not only on account of its 

 swollen nature, but also by reason of its bleached appearance due 

 to the absence of chlorophyll. 



The needles at first increase evenly in thickness on every 

 side, but before long the swelling becomes confined on the inner 

 (ventral) side, since this faces the main axis, which is also swelling, 



