680 Journal of Agricultural Research vol. xx, No. 9 



existence there of strains or species of Sclerospora as yet unrecognized ; 

 but what their relationship and significance may be, future investigation 

 must determine. 



The relationship of these two Philippine conidial forms to the oogonial 

 stage characteristic of the genus is as yet unknown. Whether Sclero- 

 spora philippinensis or Sclerospora spontanea is connected with the oogonial 

 stage which is so common on Saccharum spontaneum throughout the Philip- 

 pine Islands is yet to be established. The writer has attempted to germi- 

 nate the oogonia of the latter and to obtain inoculations with them, but so 

 far he has been unsuccessful. Until the precise connection is definitely 

 established, it is well to be cautious about assuming that the two types 

 of spores are with certainty different phases of the same species. It 

 may be worthy of note that the writer has found, in addition to the oogonia 

 on Saccharum spontaneum, similar spores on Miscanthus japonicus and 

 on cultivated sugar cane in the mountains of northern Luzon. On all 

 these hosts the oogonia are apparently the same species; and their 

 significance and importance will be discussed by the writer in a later 

 paper. 



NONSPECIALIZATION 



As the problem now stands, the Philippine maize-mildew presents an 

 interesting situation, since it involves two causal Sclerosporas quite distinct 

 morphologically but practically indistinguishable physiologically both in 

 their effect on, and in their virulence to, a range of hosts. The genus 

 Sclerospora seems, then, to present a marked contrast to the strong 

 specialization of the closely related genus Peronospora. In the latter, 

 the work of Gaumann (5, 6, 7) has shown that the species are strongly 

 specialized, being distinct on different hosts. This is true especially in 

 the Rubiaceae (7), but also to a marked degree in the Cruciferae (5) and 

 the Scrophulariaceae (6). The distinction holds both morphologically, 

 in the size and character of the conidiophores and conidia, and also 

 physiologically, in their inability to infect any host species but that from 

 which the spores were derived. Gaumann, therefore, regards it as highly 

 improbable that the same host species would be found to harbor more 

 than one species of Peronospora. In Sclerospora, however, we have 

 the two species, Sclerospora spontanea and 5. philippinensis, morpho- 

 logically distinct, yet both with equal ease inoculating the same series of 

 hosts, including members not only of the Maydeae but also of the Andro- 

 pogoneae. 



SIGNIFICANCE OF OCCURRENCE 



The finding of Sclerospora spontanea on a wild gramineous host is of 

 interest. Hitherto in spite of the attention which the destructive 

 oriental Sclerosporas have attracted, no conidial representative of the 

 genus has ever been reported as occurring naturally upon a wild host. 

 It is a question whether the occurrence of Sclerospora spontanea on wild 



