682 Journal of Agricultural Research vol. xx. No. 9 



fields adjacent to or even interplanted with infected maize, should be the 

 only one to succumb. 



The matter is still further complicated by the fact that in Formosa 

 Miyake easily obtained the infection of sugar-cane plants grown from 

 cuttings, while in the Philippines the writer was not able to inoculate 

 cutting-grown plants of sugar cane, or even of Saccharum sponianeum, 

 although seedlings of this grass were readily infected (PI. 78, A). More- 

 over, in Formosa the effect of Sclerospora sacchari Miyake on sugar cane 

 is far more destructive than was the effect of Sclerospora spontanea on 

 this single cane plant. In the former the elongation and weakening of 

 the shoots and the conspicuous yellowish striping of the leaves are a dis- 

 tinct contrast to the stunting of the shoots and faint, pale green markings 

 of the leaves which characterized the Philippine specimens. Also, 

 although the latter died shortly after being transplanted, this was ap- 

 parently due to the severe treatment they had received rather than to 

 the destructive character of the Sclerospora. It is possible that Sclerospora 

 spontanea, in its essential individuality, is much less virulent to sugar 

 cane than Sclerospora sacchari, or it may be that some limiting factor is oper- 

 ative in the Philippines. The work of Fawcett (4) indicates that tempera- 

 ture differences may exercise an important limiting effect within a smaller 

 geographic range than from Cebu to Formosa. In any case, although 

 the matter is in need of further study, it can safely be said that in so far 

 as has been observed in the Philippines the production of sugar cane is 

 unaffected by Sclerospora spontanea or other conidial Sclerosporas. 



SUMMARY 



The downy mildew of maize which is extremely destructive in the 

 Philippine Islands has been found to be caused by the Peronosporaceous 

 genus Sclerospora. At first only one species was thought to be involved, 

 and this was described by the writer as Sclerospora philippinensis . More 

 recently the problem presented by the Philippine maize-mildew has been 

 still further complicated, since a second causal species of Sclerospora has 

 been found to be concerned also. The foregoing paper describes this 

 species as new {S. spontanea) and presents briefly its morphological and 

 physiological characteristics and its importance and relationship. 



Sclerospora spontanea, the more recently discovered form, occurs in the 

 Islands of Cebu, Bohol, and Leyte, where it was found on the wild grass 

 Saccharum spontaneum L., on sugar cane (Saccharum ofjicinarum L,.), 

 and on maize (Zea mays L.). Sclerospora philippinensis, the species 

 first recognized, occurs in the Island of Luzon, where it was found on 

 maize, teosinte (Euchlaena luxurians Schrad.), and sorghum (Andropo- 

 gon sorghum [L.] Brot.). 



Morphologically, Sclerospora spontanea is characterized by the rela- 

 tively much greater length and slenderness of its conidiophores in general 

 and of its basal cells and conidia in particular. In these respects it 

 differs markedly from 5". philippinensis, which has shorter, stockier 



