64 Leaf Character hi Reverted Black Currants 



difference in addition to that readily perceived by the eye in the living 

 specimen. 



Unless the isolated mite infection in bud 13 be responsible for the 

 sudden drop into the more reverted state there appears to be no reason- 

 able explanation. 



From this point onwards the recovery continues unchecked. The 

 20th, 23rd and 25th leaves are shown in Figs. 37-39, the latter being 

 normal in vein number and nearly normal in margin. 



Case 8. This was a reverted shoot from a half cut down bush ex- 

 amined on August 5th. The rest of the bush appeared normal. Here 

 again, though the base of the shoot was mite infected, the first six leaves 

 were in every way normal with a vein number of six. Reversion started 

 quite suddenly at the 7th leaf on six buds in front of the first infected 

 bud. The vein number suddenly dropped to four and the margin became 

 reverted. Reversion gradually increased up to the 15th leaf with a vein 

 number of two, after which a partial recovery to four set in for four buds, 

 followed by further reversion to the end attended by the characteristic 

 "oak leaf." As judged by the leaf vein number and margin, " oak leaves" 

 appear to be merely an accentuated stage of reverted leaves. Such leaves 

 (though not belonging to this series) are shown in Figs. 44-46. 



The chief differences between case 8 and 7 are two in number. In 

 Graph 7 the curve, with the exception of one bud, follows the general 

 curve of reversion, the latter half having a general rising tendency. In 

 Graph 8, though a short recovery begins at leaf 16, the general ten- 

 dency of the latter part of the curve is downwards instead of upwards. 

 The second point is that two isolated infected buds occurred after the 

 basal infection. These were very slight as each only contained one mite. 



Case 9. This was from an Ogden's Black bush with plenty of old 

 big bud on the bush and was examined on August 6th. 



This case shows in its graph the same sort of curve as does case 7, 

 but there are no mite infected buds after the usual basal ones and the 

 curve is of the same order as a reverted one unaffected by mites (of 

 Graph 3). It is, however, different in that it drops lower, reaching a 

 vein number of two, and also fails to reach so high a number at the end 

 of the graph. Instead of attaining at this point a vein number of six or 

 seven it scarcely reaches five and the leaf instead of being "normal" 

 as in Graph 3 never gets beyond "normal in shape, but slightly reverted 

 in margin." Though therefore of the same order as Graph 3 it is of 

 different intensity and this difference may provisionally be referred to the 

 mite infestation which is the only visible difference between the two shoots. 



