90 PLANT DISEASES 



PEAR LEAF BLISTER 



(Taphrina bullata, Tul.) 



This fungus often causes irregularly shaped, thickish 

 Blisters or swollen patches to appear on pear leaves. 

 Quince leaves are also stated to be sometimes similarly 

 attacked. The blisters are green at first, then dark brown, 



Fig. 13. Taphrina bullata. i, leaf of pear-tree with blisters 

 caused by the fungus ; 2, asci with spores seated on the epidermis 

 of a leaf, x 300. 



and finally become delicately frosted on the under surface 

 with the fruit of the fungus, which bursts through the 

 cuticle. The leaves do not curl as in the 'leaf curl' of 

 the peach, but remain flat. 



PREVENTIVE MEANS. The mycelium is not perennial 

 in the branches of the host-plant in the species of Taphrina, 

 as is the case with the species of Exoascus, hence its 



