FUNGI IMPERFECTI 297 



Ramularia rufomaculans Pk. This Ramularia produces on the 

 leaves of buckwheat (Fagopyrum esculentum} blotch-like areas cov- 

 ered with abundant conidiophores. In appearance it is therefore 

 very much like the form on cotton. 



VIII. CERCOSPORELLA 



Cercosporella Persicae Sacc. The frosty mildew of the peach in 

 the United States is far more common from Maryland southward. 

 It forms on the under surfaces of the leaves conidiophores and 

 conidia in such quantity as to give the appearance of a surface 

 mildew. It is most prevalent and often a serious disease in moist 

 regions, but may be readily controlled by early spraying. 



IX. RICE BLAST 

 Piricularia grisea (Cke.) Sacc. 



FULTON, H. R. Rice Blast. La. Agl. Exp. Sta. Built. 105: 1-12. figs. 1-12. 



1908. 



FARNETI, R. Rivista Patalog. Veg. 2 : 1-11,17-42. 

 METCALF, HAVEN. Preliminary Report on the Blast of Rice. S. C. Agl. 



Exp. Sta. Built 121 : 1-43. 1906. 



Habitat relations. The blast of rice (Oryza sativa) is reported 

 from the most important rice-growing regions, and would appear 

 to be a common disease wherever rice is cultivated. It causes no 

 small annual loss, and the outbreaks are frequently severe. Up to 

 the present time there is very little unanimity in the opinions ex- 

 pressed with respect to the factors conditioning epidemics. After 

 an analysis of diverse conditions reported as operative, Fulton 

 believes that the factors are far more complex than generally 

 stated. In South Carolina it seemed that unfavorable soil con- 

 ditions are important, and in Italy lack of root aeration is sug- 

 gested as the cause of "brusone," a disease with which the 

 Piricularia is at least associated. 



Under favorable conditions there is a marked difference in the 

 susceptibility of diverse rice varieties. At the present time it would 

 seem that there are no varieties wholly free from the disease. 



Symptoms. The fungus attacks leaves and stems. Upon young 

 plants the older leaves are first affected and later the younger por- 

 tions of the plant. The young leaves become rapidly pale in the 



