480 
POPULAR SCIENCE REVIEW. 
The “blight” or “mildew” which occurs on the common hedge- 
maple, as well as on the sycamore leaves, is exceedingly con- 
spicuous when occurring on the former plant. The whole 
hush often presents 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 hoary from 
another cause. The whiteness occurs in patches, has often a 
pinkish or violaceous tint, and glistens like hoar frost. This 
affection of the leaves was, at one time, believed to be pro- 
duced by a fungus which was called Erineum acerinum , but 
now it is regarded as a diseased state of the tissues. In the 
maple mildew, both surfaces of the leaves are alike affected, 
and the little, dark, point-like conceptacles will be found 
studded over both. It is not uncommon to meet with very 
white leaves, caused by the mycelium, but which bear no fruit. 
The appendages in this species are shorter than in the last (fig. 
10), and the tips are bifid (fig. 11), or divided into two short 
branches, each of which is bifid, and uncinate or hook-shaped 
(fig. 12). The conceptacles contain not less than eight spo- 
rangia, each of which encloses eight spores. 
Amongst the parasites that prey upon the much-abused 
berberry (which has been charged in turn with producing the 
mildew in corn), is one which causes the green leaves to assume 
a chalky appearance (fig. 14), though less conspicuously than 
in the maple blight. This parasite is the berberry mildew 
( Micro spliceria berberidis , Lev.). In such localities as the 
writer has met with the berberry suffering from mildew, he 
has invariably found a larger proportion of leaves with the 
barren mycelium than of those on which the conceptacles 
were developed. Perhaps in other localities this may not be 
the case. The appendages, as will be seen on reference to our 
plate, differ materially from any of those to which we have 
referred ; indeed, this genus (or sub-genus) has the most ela- 
borate and beautiful forms in these appendages of any of the 
Erysiphei. A figure is given of the tip of a fulcrum from a 
continental species (M. Ehrenbergii, Lev.), not yet found in 
this country (fig. 18). In the berberry blight the appendages 
are straight at the base, but afterwards become forked, each 
fork being again forked, and these yet again branched in a 
similar manner (fig. 16) ; so that a complex dichotomous tip is 
formed to each of the appendages (fig. 15). Each conceptacle 
contains about six sporangia, and each sporangium contains 
from six to eight spores (fig. 17). 
The common gooseberry is also liable to a visitation from an 
allied species, in many respects closely similar, but differing in 
having the tips of the appendages more branched, and the 
extremities of the ultimate branclilets are not entire and at- 
