Feb. i,i 9 2i Another Conidial Sclerospora of Philippine Maize 683 



conidiophores, shorter, thicker basal cells, and shorter, broader conidia. 

 There are, moreover, some minor distinctions between the branch sys- 

 tems and between the sterigmata of the two species. 



These differences remain constant for each species and are not influ- 

 enced by growth on different hosts even through several generations. 

 Both species have been artificially inoculated with equal ease from one 

 to another of the following hosts : Maize, teosinte, Miscanthus japonicus, 

 and Saccharum spontaneum. Attempts to inoculate sorghum artificially 

 were unsuccessful with both species. Because no seedlings of sugar 

 cane were available, no inoculation with either fungus was attempted. 

 Inoculations on sprouted sugar-cane cuttings were uniformly unsuccessful. 



Since the size and shape of the conidia are the most useful criteria of 

 interspecies distinction, they are given in detail. Measurements of 700 

 conidia of each of the two species were combined into comparative tables 

 and graphs of frequency distribution in an attempt to present the dif- 

 ferences between them quantitatively as well as qualitatively. 



Although morphologically the two species differ as has been described, 

 yet physiologically, in general effect in the field, in effect on the individual 

 plant, and in virulence to the same wide range of hosts no distinction 

 between them is apparent. 



The discovery that two forms are involved complicates the problem 

 presented by the Philippine downy mildew of maize. Because two 

 forms morphologically different but practically indistinguishable in 

 physiologic effect are concerned in the same disease, there appears to 

 be a decided lack of that specialization which characterizes certain other 

 genera of the Peronosporaceae. It seems highly probable that still 

 other forms will be found to be concerned in similar diseases in the 

 Philippine Islands and throughout the Orient. 



In addition to these two conidial species with a host range of maize, 

 teosinte, sorghum, sugar cane, Saccharum spontaneum, and Miscanthus 

 japonicus, the writer has encountered in the Philippines oogonial stages 

 of Sclerospora on Saccharum spontaneum, Saccharum ofjicinarum, and 

 M. japonicus. The oogonia on these three hosts are practically indis- 

 tinguishable. Whether these oogonial and conidial stages are quite 

 unrelated or are indeed only phases in the development of the same 

 organism remains to be determined. 



Sclerospora spontanea, like 5. philippinensis, is closely related to the 

 other conspicuous conidial Sclerosporas of the Orient: 5. javanica Palm, 

 of Java; 5. maydis (Rac.) But., of India; and 5. sacchari T. Miyake, of 

 Formosa. All these forms are characterized by the predominance of 

 the conidial stage, the absence or great rarity of the oogonia, germina- 

 tion of the conidia by tubes, and the occurrence on maize, sugar cane, 

 and related hosts in the Orient. 5. spontanea, however, because of its 

 longer, more slender spores is as a species distinguished even more 

 sharply than 5. philippinensis from these other oriental representatives. 



