170 



more inclined to produce suckers, which are a source 

 of some annoyance. 



Blistering of Leaves, — Peach trees, especially if 

 growing on ill-drained soils, are excessively liable to 

 have blistered leaves, attended by a contraction of the 

 midrib, and, in some instances, it extends to an unna- 

 tural thickening of the upper parenchymatous plate 

 of the leaves. The French gardeners term this 

 disease la cloque. We are inclined to the opinion 

 that this disease arises from an excess of moisture 

 being imbibed by the roots. An effort is made by 

 the tree to enlarge its leaves for the elaboration of 

 this excessive and diluted supply of sap, and in the 

 effort the parenchyma of the leaves extends more ra- 

 pidly than their ribs. Contortion is thus unavoidably 

 induced. In a similar mode the pulp or parenchyma 

 of the plum and cherry cause their cuticles to burst 

 in wet weather. Acari frequently make their appear- 

 ance upon such leaves, but these are attendants upon 

 vegetable disease, not the cause. Thorough under- 

 draining will probably prevent a recurrence of the 

 evil ; and in confirmation that the disease arises from 

 excessive moisture, we may observe that the diseased 

 leaves drop off, and none others occur so soon as the 

 dry hot weather of summer is fairly established. Al- 

 though, frequently, only some trees out of several 

 against the same wall are thus diseased, this proves 

 no more than that the unaffected trees are either 



