INFLUENCES AND EFFECTS. 225 
determine from the description what this so-called Ustilago may 
be, which was said to have affected a considerable portion of the 
standing rice crop in the vicinity of Diamond Harbour. 
Bunt is another pest (Zvllctia caries) which occupies the 
whole farinaceous portion of the grains of wheat. Since 
dressing the seed wheat has been so widely adopted in this 
country, this pest has been of comparatively little trouble. 
Sorghum and the small millets, in countries where these are 
cultivated for food, are liable to attacks from allied parasites. 
Ergot attacks wheat and rice as well as rye, but not to such an 
extent as to have any important influence upon the crop. Two 
or three other species of fungi are sometimes locally trouble- 
some, as Dilophospora graminis, and Septoria nodorum on wheat, 
but not to any considerable extent. In countries where maize is 
extensively grown it has not only its own species of mildew 
(Puceinia), but also one of the most enormous and destructive 
species of Usézlago. 
A singular parasite on grasses was found by Cesati in Italy, 
in 1850, infesting the #inmes of Andropogon.* It received the 
name of Cerebella Andropogonis, but it never appears to have 
increased and spread to such an extent as was at first feared. 
Even more destructive than any of these is the potato 
diseaset+ (Peronospora infestans), which is, unfortunately, too 
well known to need description. This disease was at one time 
attributed to various causes, but long since its ascertained source 
has been acknowledged to bea species of white mould, which 
also attacks tomatoes, but less vigorously. De Bary has given 
considerable attention to this disease, and his opinions are 
clearly detailed in his memoir on Peronospora, as well as in his 
special pamphlet on the potato disease.{ One sees the cause of 
the epidemic, he says, in the diseased state of the potato itsclf, 
produced either accidentally by unfavourable conditions of soil 
and atmosphere, or by a depravation that the plant has experi- 
* «Gardener's Chronicle” (1852), p. 643, with fig. “ 
+ Berkeley, ‘‘On the Potato Murrain,” in ‘‘Jour. Hort. Soc.” vol. i, (1846), 
p. 9. 
t De Bary, ‘‘ Die gegenwartig herrschende Kartofie] krankheit.” 
11 
