1 1 6 Journal of A gricultural Research vot. xix. No. 3 



by 17 /x in diameter, and comparatively few showing the shortness which 

 marks the Javan form. Moreover, although the field characters of the 

 two diseases are very similar, the Javan Sclerospora presents an addi- 

 tional point of difference in that it does not attack teosinte, although 

 teosinte-maize hybrids are, if anything, even more susceptible to it than 

 maize itself {19). 



To Sclerospora sacchari T. Miy., of Formosa, the Philippine maize 

 mildew shows a very close resemblance in the size, the form, and even 

 the minor structural characteristics of the conidiophores. Also, the 

 conidia of the two forms are evidently quite similar, since the illustra- 

 tions and the description (ellipsoid or oblong with rounded apex, 25 to 

 41 /x long by 15 to 23 )U in diameter) of the Formosan conidia are appli- 

 cable to those of the Philippine species also. A marked difference be- 

 tween the two, however, is shown in their virulence on various hosts, 

 for, while Sclerospora sacchari grows on both maize and teosinte as does 

 the Philippine Sclerospora, still the former attacks sugar cane of many 

 varieties, including those grown most commonly in the Philippine Islands, 

 with violent intensity, while the latter, so far as is known, does not infect 

 that crop at all. In the Philippines, in regions heavily infected with 

 the maize-mildew, sugar-cane fields comprising many varieties grown 

 under widely varying conditions and situated adjacent to the badly 

 infected maize, and even containing some maize plants growing among 

 and in contact with the young cane, have been under frequent observa- 

 tion during all stages of their development for over a year, and yet no 

 case of infection with the downy mildew of maize has ever been seen. 



Moreover, inoculation experiments such as were successful with maize, 

 teosinte, and sorghum have so far failed to cause infection of the Philip- 

 pine Sclerospora of maize on sugar-cane varieties found susceptible to 

 the Formosan disease. Furthermore, the oogonial stage which has been 

 reported for Sclerospora sacchari T. Miy. forms an additional point 

 wherein it differs from the Philippine fungus, although it should be noted 

 that the oogonia, which have been found only once and are not figured, 

 have not been proved to be connected with the conidial stage of Sclero- 

 spora sacchari. 



On comparing the Philippine downy mildew of maize with the British 

 Indian species {Sclerospora maydis (Rac.) But.), with which it has been 

 regarded as identical, a close resemblance indeed is apparent. The 

 conidia especially are similar in both shape and size in so far as one can 

 judge from the data available; the lack of any other type of spore 

 is another point of agreement. In considering the conidiophores of the 

 former, however, it should be noted that the description, dimensions, 

 and illustrations indicate that the material was imperfect, for if one may 

 judge from the Philippine fungus, the size and the abruptly ending base 

 of the conidiophore signify that the main axis had been broken off just 

 above the basal cell. Any accurate comparison, therefore, is difficult. The 



