A. H. Lees 65 



Case 10. This and the following one have been selected as special 

 cases likely to throw light on the possible effect of mite infestation at the 

 base. In both the shoot has ceased growth during the summer and a 

 subsequent fresh growth has started from a bud later on. Case 10 was 

 from a badly mite infested bush. It possessed five primary shoots of the 

 current year and all contained mites in the terminal bud. 



The particular shoot (10 in Table II) was examined on August 10th 

 and bore twelve lateral buds, one of which, number nine, had subse- 

 quently grown out later in the season after the primary shoot had ceased 

 growing. The graph for the primary shoot (Graph 10) showed a very quick 

 descent to zero and reversion was so marked at the end that the leaves 

 were strongly "oak leaf." If the hypothesis be accepted that mite 

 infection produces reverted leaves, this was to be expected as the whole 

 shoot was heavily infected. The secondary growth from bud 9 is shown 

 in the lower half of number 10 in Table II. The first point to be noted 

 is that bud 2 contained four mites. This was probably not a direct in- 

 fection, but represented the residual mites in bud 9 of the primary shoot. 

 It was probably due to the weakness of the infection that this bud grew 

 out when growth conditions became urgent and not any other bud. The 

 next point to be noted is that all the leaves are of the reverted type, 

 though not so reverted as to become truly "oak leaf." The leaf vein 

 number hovered about 2 + and showed no sign of a definite rise towards 

 the end of the graph. The lower figure for bud 2 is probably due to 

 temporary reversion due to growth conditions as indicated in the first 

 part of this paper. 



The conclusion that appears to be indicated is that this secondary 

 shoot, though practically mite free and possessing none in the terminal 

 bud, was under the influence of some special factor and that this factor 

 was the high mite infestation of the primary shoot. 



Case 11. This was from a young bush not heavily mite infected and 

 examined August 31st. Its first seven leaves were normal with a high 

 leaf vein number. Reversion began fairly suddenly at leaf 9 the margin 

 showing up quite suddenly and the vein number quickly following 

 in the next few leaves. Leaves 13 and 14 marked the bottom of the 

 curve with a vein number of 2 + . From there, for four leaves the vein 

 numbers and margin improved somewhat till at leaf 18 the shoot had 

 ceased its first summer growth. As in the case of shoot 10, later on in the 

 season a fresh growth began but this time it came from the terminal. 

 This is of course the bud where one woidd expect a fresh growth, if 

 anywhere, and no doubt it would have occurred from here in case 10 



Ann. Biol, ix 6 



