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POPULAR SCIENCE REVIEW. 
enclosing a definite number of spores (figs. 3, 5, 9, 13, &c.), 
which vary in different species. In the hazel mildew, for 
instance, there are two spores in each sporangium ; in the willow 
mildew, four; in the maple mildew, eight; in the grass mildew, 
and some others, numerous. The tips of the appendages are 
variable, and often elegant (figs. 8, 11, 12, 16, 18, and 19), 
sometimes simple and at others symmetrically branched. All 
the species occur on the still living and green parts of plants, 
especially the leaves, and are therefore truly parasitic. A 
pocket lens will show whether any conceptacles are present on 
any suspicious leaf which may be collected, but high powers of 
the microscope are essential for their complete examination. 
It is during autumn when vegetation begins to languish, that 
we shall be most successful in searching for specimens. They 
will then be found almost everywhere, and the white mycelium 
forms an object too conspicuous for them to be readily over- 
looked. Botanically, nearly all the species were at one period 
included in one genus, under the name of JErysiphe, a name 
derived from the Greek, and signifying “ mildew ; ” at the 
present time they are distributed through several genera, the 
chief distinctions of which are based upon the form of the 
appendages. Though personally disposed to question the 
generic value of such distinctions, it would be imprudent to 
adopt any other names here than those to be found in recent 
English works on fungi. 
The first species in our enumeration is found on cultivated 
roses. What a deplorable picture does a favourite rose-bush 
present when attacked by this mildew ? The leaves blistered, 
puckered, and contorted; their petioles and the peduncles 
and calyces of the flowers swollen, distorted, and grey with 
mould ; the whole plant looking so diseased and leprous, 
that it needs no mycologist to tell that the rose is mildewed. 
The conceptacle in this species is minute and contains but one 
sporangium, which is one of the characters of the genus in 
which it is now included, and a more justifiable distinction 
than the ramifications of the appendages. The mycelium is 
rather profuse, and the threads or appendages which spring 
from the conceptacle are simple and floccose (fig. 2). The spo- 
rangium contains eight ovate spores. This species [Splicer otheca 
pannosa ), in its oidioid or conidiiferous form was for some time 
known under the name of Oidium leucoconium. 
An allied species constitutes the hop-mildew, a visitation 
with which some of our Kentish friends are too familiar. This 
is not a prejudiced species in the choice of its habitation, since 
it is found on many other plants, where it flourishes with equal 
vigour. The meadow-sweet, burnet, scabious, teasle, dandelion, 
and other composite plants, plantain, and plants of the cucumber 
