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- 

 xpora 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 TucJceri, B.j 

 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 Spharotheca Castagnei, Lev., 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 tho 

 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., oft6n successful in spoiling beds of 

 celery by attacking the leaves ; Cystopus candidus. Lev., and 

 OlfBOSporium concentricum, Grev., destructive to cabbages and 

 other cruciferous plants ; Trichobasis Fabce, Lev., unsparing 

 when once established on beans ; Erysiphe Martii, Lev., 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. 



