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 (Tillctia, caries} which occupies the 

 whole farinaceous portion of the grains of wheat. Since 

 dressing the socd 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 Diloplwspora 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 

 (Puccinid), but also one of the most enormous and destructive 

 species of Ustilago. 



A singular parasite on grasses was found by Cesati in Italy, 

 in 1850, infesting the glumes of Andropogon* It received the 

 name of Cerelclla 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 

 disease t (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 be a 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. J One sees the cause of 

 the epidemic, he says, in the diseased state of the potato itself, 

 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. 



f Berkeley, "On the Potato Murrain," in "Jour. Hort. Soc." vol. i. (1846), 

 p. 9. 



$ De B^ry, "Die gegenwartig herrschen.de Kartoffelkrankheit." 

 11 



