INFLUENCES AND EFFECTS. 227 
of inducing decomposition, a fact which has been fully confirmed 
by Berkeley. 
Unfortunately there are other species of the same genus of 
moulds which are very destructive to garden produce. Perono- 
spora gangliformis, B., attacks lettuces, and is but too common 
and injurious. Peronospora effusa, Grev., is found on spinach 
and allied plants. Peronospora Schleideniana, D. By., is in some 
years very common and destructive to young onions, and field 
crops of lucerne are very liable to attack from Peronospora 
trifoliorum, D. By. 
The vine crops are liable to be seriously affected by a species 
of mould, which is but the conidia form of a species of Erysiphe. 
This mould, known under the name of Oidium Tuckeri, B., 
attacks the vines in hothouses in this country, but on the Conti- 
nent the vineyards often suffer severely * from its depredations ; 
unfortunately, not the only pest to which the vine is subject, for 
an insect threatens to be even more destructive. 
Hop gardens suffer severely, in some years, from a similar 
disease ; in this instance the mature or ultimate form is per- 
fected. The hop mildew is Spherotheca Castagnei, Lév., which 
first appears as whitish mouldy blotches on the leaves, soon 
“becoming discoloured, and developing the black receptacles on 
either surface of the leaf. These may be regarded as the 
cardinal diseases of fungoid origin to which useful plants are 
subject in this country. : 
Amongst those of less importance, but still troublesome 
enough to secure the anathemas of cultivators, may be men- 
tioned Puccinia Apii, Ca., often successful in spoiling beds of 
celery by attacking the leaves; Cystopus candidus, Lév., and 
Gleosporium concentricum, Grev., destructive to cabbages and 
other cruciferous plants; Zrichobasis Fabe, Lév., unsparing 
when once established on beans ; Erysiphe Martii, Lév., in some 
seasons a great nuisance to the crop of peas. 
* “Reports of H. M. Secretaries of Embassy and Legation on the Effects of 
the Vine Disease on Commerce, 1859 ;” ‘‘Reports of H. M. Secretaries of 
Embassy, &c., on Manufactures and Commerce, Vine Disease in Bavaria and 
Switzerland, 1859,” pp. 54 and 62, 
