DISEASES. 451 



Pear-leaf Blight. This disease has already been al- 

 luded to in treating of pear seedlings. It is a sort of 

 rust that appears on the leaves in July or August, first as 

 small brown spots ; these spread rapidly over the leaves 

 until they arc completely dried up and growth stopped. 

 It appears in a certain spot as a center, from which it 

 spreads. Whether it be an insect, a fungus, or some at- 

 mospherical cause that produces this blight, is unknown. 

 Certain cases favor one or other of these opinions. More 

 minute investigations are wanted on the subject. 

 * To avoid its evil effects as far as possible, the great 

 point is, to get a rapid, vigorous growth, before mid-sum- 

 mer, when it usually appears. Seedlings grown in new 

 soils do not appear to be so much affected as in old. 

 Where stocks are affected very early in the season, they 

 become almost worthless, on account of the , feebleness 

 produced in both stem and roots by such an untimely and 

 unnatural check. Some special applications, such as coal 

 cinders, iron filings, copperas, etc., have been suggested, 

 but no evidence has yet been produced of their efficacy. 



The Gum in Stone Fruits. The cherry, plum, apricot, 

 and peach are all more or less subject to this malady. 

 The cherry is particularly liable to it in the West. It is 

 produced by different causes, such as a wet soil, severe 

 pruning, pruning at an improper time, violent changes of 

 temperature, etc. The gumming of the Cherry in the 

 West is considered by some to be owing in a great mea- 

 sure to the bark not yielding naturally to the growth of 

 the wood, and hence they practise longitudinal incisions 

 on it. The dhcrry-tree has a very powerful bark, and in 

 some cases it may not yield naturally to the expansion or 

 growth of the wood. We have seen about a foot of the 

 trunk of a cherry-tree several inches smaller than the 

 parts both above and below it. The bark was as smooth 

 as glass on it, the first rind being unbroken, whilst on the 

 large parts this was quite rough. This was a case arising 



