TREES AND SHRUBS 



mostly confined to the tips of the shoots, causing them to become brown 

 and shrivelled. The life-history resembles that of the previous speeies. To 

 combat the attack spray with potassium sulphide, one ounce to two gallons 

 of water, repeating every ten days till the fruit is nearly mature. 



Peach-leaf Blister or "Curl," Exoascus deformans, causes the leaves to 

 become blistered and contorted in various ways, presenting an appearance 

 as though suffering from an attack of aphis. Such a case of distortion might 

 well have been placed in the chapter on Galls, especially as the curling of 

 the leaves is often accompanied by an abnormal swelling of the young 

 shoots, but owing to the serious nature of the disease we have preferred to 

 describe this and some few others as true Fungoid Pests. The fungus in 

 this instance causes the under surface of the leaves, in the hollows of the 

 blisters, to assume a hoary or frosted appearance, the interior being closely 

 packed with cylindrical cells, or asci, containing sporidia, the whole being 

 covered with a transparent membrane. 



Diseased or fallen leaves should be burned. The mycelium is perennial 

 in the branches, following the young growth, producing the disease in 

 the leaves each year, and preventing the ripening of the wood. Branches 

 bearing diseased leaves should be pruned back beyond the point of in- 

 fection. 



Pear-leaf Cluster-cups, Rasstelia cancellata, is a parasite which thickens 

 Pear leaves at the infected spots by the internal growth of the mycelium, 

 and the " cups " are flask-shaped brown bodies containing secidiospores. The 

 cups, or peridia, split into numerous thread-like filaments, which for some 

 time are united at the apex. The diseased leaves fall early in the autumn, 

 resulting in a lack of reserve food for the following season, and if the attack 

 occurs two or three years in succession, the tree will probably perish. All 

 diseased leaves should be burned. By some authorities the Puccinia gene- 

 ration of this disease is said to be found in the Savin Jelly-rust. 



Pear-leaf Blister, Exoascus bullatus, or Taphrina bullata, distorts the 



foliage in a similar manner to the "curl" on Peach leaves, but in this case 



the leaves remain flat. All blistered leaves should be burned, to check re- 



lxviii 





