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attacks tke stem, and ultimately the tuber. For examination, 
it is better to select the leaves soon after the fungus makes its 
appearance. 
Turnip Mould. — Since the advent of the potato murrain a 
similar disease has been witnessed, though more limited in its 
extent, amongst Swedish turnips, commencing in little waved 
irregular lines following the course of the vessels, around 
which spots are formed by the deposition of dark granules, 
in the same manner as in the potato. In this instance, the 
leaves apparently are first attacked in a similar manner by a 
species of mould or Peronospora allied to the one already 
described, but which has been long known as parasitic upon 
cruciferous plants, to which the turnip belongs. This species, 
termed Peronospora parasitica, is white in all stages of its 
growth. It is much more branched, and the branches are 
comparatively shorter than in the potato mould, and the tips 
of the branches are bifid (fig. 1). The spores are very large and 
globose, features also which distinguish this mould from the last. 
A short time since we were called to witness a bed of splendid 
cauliflowers, which had, up to that time, been the pride of 
their cultivator ; but, alas ! their glory was threatened with 
speedy annihilation, for in nearly every instance the lower 
leaves had become more or less covered on their upper sur- 
face with yellow spots, and beneath, glaucous with the mould 
we have been describing. The diseased leaves were all imme- 
diately removed, but we fear without success, although no 
positive information has since reached us. The almost un- 
natural vigorous green of the leaves, prior to the appearance 
of the mould, is not at all an uncommon occurrence : this 
phenomenon has been noticed in the ears of corn, in which 
every grain was soon afterwards filled with spores of bunt. 
Onion Mould. — Another disease, produced by Fungi of the 
same genus, has made its appearance upon young onion plants 
in the spring. The mould is called Peronospora destructor , 
and has many features in common with those already de- 
scribed. In this instance the threads are greyish and erect, 
with alternate branches, not divided by transverse septa, and 
the spores are obovate, attenuated towards their base (fig. 2). 
This mould, in some years, is very common and destructive, by 
preventing the young plants which are attacked from coming 
to perfection. It is not confined to the onion, but appears on 
other allied species of Allium (to which the onion belongs). 
The threads form large patches or blotches on the leaves, and 
sometimes cover them entirely. It very much resembles the 
turnip mould, from which the form of the spores considerably 
differs. Doubtless this, as well as all the other species of mould 
alluded to in this paper, are most common and destructive in 
