A. H. Lees 61 



from a bush cut right down to the ground. Case 5 was not investigated 

 for mite while none was found in case 6. 



These two are considered together because their graphs (5 and 6) 

 run practically together. Roughly speaking, only half the typical rever- 

 sion curve, namely, the ascending half (of Graph 3), is represented. 

 The reason that the first part of the curve is missed is probably this. 

 Being hard cut back to weak buds growth starts relatively late in the 

 spring and then is particularly vigorous owing to the upsetting of the 

 balance between root and shoots. The late start also tends in the same 

 direction, as general growth conditions are then fast approaching their 

 maximum. However, the recovery of the venation is complete, in each 

 case 6 or 6 + being attained. In one of these cases at least the issue 

 was not directly affected by mite. 



Case 7. In this and the following cases the position is complicated 

 by the presence of mites in appreciable quantities. 



In Table II the buds containing mites are indicated and an approxi- 

 mate figure given to indicate quantity. 



In the graphs mite attack is indicated by a x , but the position has 

 been shifted in each case to four buds in advance of the one actually 

 affected. 



In Table II, No. 7 it is seen that the most basal bud was mite free, 

 and that the next four buds were fairly heavily infected. The veins 

 remained five and the margin normal until the sixth which shows a 

 slightly reverted margin and the seventh which shows a definite drop 

 in vein number below normality, a drop which was subsequently con- 

 tinued. If the mite infection therefore has anything to do with the 

 production of reverted foliage no effect was produced until the fourth 

 leaf subsequently produced. For this reason in the graphs of 7-11 the 

 position of the mite infected bud has been marked four leaves forward. 

 After these four big buds only single mite free buds were found for a 

 space of four more buds and reversion gets steadily more marked up to 

 the twelfth leaf which has a venation number of one and a deformed 

 appearance. The next leaf which is four leaves from the last big bud has 

 begun to recover and subsequent leaves up to 18 continue this gradual 

 recovery, the vein number by this time being four and the margin 

 distinctly "less reverted." The leaf following shows a sudden drop of 

 vein number to three and the margin becomes distinctly " more reverted." 

 The following or 20th leaf has again suddenly madfe a recovery to four 

 and "less reverted" and this recovery is continued until the end leaf 

 which has a vein number of five and a practically normal margin. 



