92 PLANT DISEASES 



POPLAR FRUIT BLISTER 



( Taphrina johansonii. Sad eb.) 



Attacks the carpels of the aspen, causing them to become 

 very much swollen and change in colour to a bright golden 

 yellow. 



ELM LEAF BLISTER 



(Taphrina ulmi^ Johans.) 



This fungus forms blisters on the leaves of the common 

 elm, and on those of the wych elm. These patches are at 

 first dark, dingy green, then blackish-brown, and often 

 cover a great portion of the leaf. 



PERISPORIACEAE 



POWDERY MILDEW OF VINE 

 (Uncinula spiralis, Berk, and Curt.) 



The conidial stage of this fungus has been known in 

 this country since 1845, when it was described by the Rev. 

 M. J. Berkeley under the name Oidium tuckeri. It is probably 

 a native of the United States, where it is common on both 

 wild and cultivated vines. The fungus forms white or 

 greyish-white patches on the upper surface of the leaves, 

 young shoots, and fruit. After the patches have been 

 present for some time, numerous short branches of the 

 mycelium grow erect, each branch becoming converted at 

 its upper part into a chain of oblong conidia. The terminal 

 conidium is the oldest, and when mature falls off, the one 



