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MILDEWS, RUSTS AND SMUTS 
the American gooseberry mildew, as both are white at first, 
and otherwise practically indistinguishable. 
Two serious epidemics are produced by species belonging 
to this genus. S. pannosa causes rose mildew, and S. 
mors-uvae, the still more serious American gooseberry 
mildew. 
UNCINULA 
The perithecium containing several asci, and the un¬ 
branched appendages with hooked or curled tips, stamp the 
present genus. The species occur chiefly on the leaves of 
trees, poplars, willows, alders, blackthorn, etc., and are 
not responsible for any serious disease of cultivated plants. 
MICROSPHAERA 
Asci several in the perithecium ; appendages with 
usually many times forked tips, the branches forming an 
elaborate and highly ornamental structure, not met with 
in any other genus. M. grossulariae is the cause of the Euro¬ 
pean gooseberry mildew, which sometimes proves injurious 
to cultivated gooseberry bushes, but by no means to the 
same extent as that caused by Sphaerotheca mors-uvae, 
which has recently over-run this country, and Europe 
generally. 
ERYSIPHE 
Perithecia containing several asci ; appendages vague 
and without any definite branching at the tip, usually 
intermixed with the mycelium. Sphaerotheca has somewhat 
similar appendages, but differs in having one ascus in the 
perithecium. In some species the spores are only formed 
in the ascus after the host-plant has been dead for some 
time. 
PHYLLACTINIA 
Perithecia large, containing many asci ; appendages 
straight, spine-like or needle-like, with a large swollen base, 
separate this genus from every other. Not uncommon 
on leaves of hazel, sycamore, alder, etc. 
PODOSPHAERA, Kunze 
Perithecia subglobose, blackish when mature ; only one 
ascus present, subglobose, 8-spored; spores elliptical, 
colourless ; appendages springing from the tip of the ascus, 
or from the middle or equatorial region, forked at the tip, 
sometimes coloured. 
Podosphaera agrees with Sphaerotheca in only having one 
ascus in the perithecium, but differs in the appendages 
