a Note on the early stages of its development. 15 



One of the first indications of the gall growth is the dis- 

 appearance of the chlorophyll, and this is at once visible to the 

 naked eye on bisecting an infected bud longitudinally. As the 

 area extends its boundaries the chlorophyll gradually recedes, and 

 at length the whole of the affected portion of the shoot appears, 

 on removal of the bud-scales, as if it had been bleached. 



Neither resin canals nor secretory cells of any description are , 

 to be found in the gall area, any that existed prior to the com- 

 mencement of gall formation having been absorbed into the gall 

 parenchyma. 



The " tannin " contained in the cells of the pith and mesophyll 

 also disappears. In microtome sections it breaks up first into 

 large granular masses, then into smaller granules, and finally 

 disappears. In cells which are still normal, this deposit of tannin, 

 after fixing with dilute Flemming, is so dense as to entirely 

 conceal all details of the protoplasm and nucleus, but wherever 

 the gall action has penetrated these details are laid bare, and the 

 cells look as if they had been treated with some clearing agent. 



One is so accustomed to connect tannin with galls that this 

 statement may at first appear doubtful. It should however be 

 mentioned that at this stage the shoot appears incapable of 

 struggling against the disease, but in the next stage, after it has 

 emerged from the bud-scales and has begun to assimilate, tannin 

 is again found in abundance. I believe however that the tannin 

 found in the later stages is of a different nature and composition 

 to the tannin present in the bud. 



The disintegration of the tannin seems to be closely connected 

 with the formation of starch which now makes its appearance in 

 great quantity. The cells round the periphery of the gall area 

 become as closely packed with starch granules as are the endo- 

 sperm cells of wheat. The quantity decreases as one proceeds 

 inwards towards the centre of the gall, and in the very centre no 

 starch or only a few scattered granules are found. 



I think a possible explanation of the origin of this starch may 

 be that the tannin contained in the pith and mesophyll cells is in 

 reality a glucoside, which on breaking down forms considerable 

 quantities of glucose, and this serves the insect for food. The 

 Glcermes however cannot absorb the glucose as quickly as it is 

 formed and the result is that the glucose solution soon reaches 

 a high degree of concentration. To reduce this concentration 

 starch is precipitated, and a molecule of w r ater is consequently 

 liberated. 



This would explain the distribution of the starch in the gall, 

 for in the centre where the apex of the proboscis lies, the glucose 

 is being continuously drawn off and would not therefore become 

 too concentrated. But the effect of this leakage would be less 



