WHITE MILDEWS OK BLIGHTS. 171 



features it is distinguished from genuine species 

 of Erysiphe. 



Two specieSj also commonj having many features 

 agreeing with each other^ are found on the leaves 

 of the maple and the willow. The willow blight 

 {Uncinida ad/wnca, Lev.) is found irrespectively on 

 various species of poplar and wUlow (fig. 221). In 

 size and external appearances, to the unaided eye, 

 it seems scarcely to differ from the preceding, but 

 more minute examination will show that in the 

 appendages there is an appreciable difference. 

 Still rigid, but no longer aciculate, the tips bent 

 or curved like a little hook, or curled upon them- 

 selves (fig. 223), radiating and numerous (fig. 222), 

 and at length tending upwards. Many sporangia 

 are contained within each conceptacle, each of 

 which is furnished with four spores. The amateur 

 must not be disappointed, if, on examining mature 

 conceptacles with a view to the discovery of the 

 sporangia, he finds only free spores. The investing 

 membrane is very delicate, and disappears generally 

 as the spores are matured. 



The " blight " or " mildew " which occurs on the 

 common hedge-maple, as well as on sycamore 

 leaves, is exceedingly conspicuous when occurring 

 on the former plant. The whole bush often pre- 

 sents a hoary appearance as if sprinkled with 

 powdered chalk. In the spring, the under surface 

 of the leaves of the same plant are liable to become 

 hoarv from another cause. The whiteness occurs 



