Feb. 1,1921 Another Conidial Sclerospora of Philippine Maize 673 



the extent of the branch system, since in cases where this is reduced and 

 the primary branches or even the main axis give rise directly to sterig- 

 mata, these sterigmata are much larger (PI 79, B) than they are when 

 arising from quaternary or tertiary branches as the ultimate structures 

 of an elaborate system (PI. 79, A). 



As a result of such differences, the conidiophore top of the Yisayan 

 Sclerospora has a more spreading, expanded appearance; and the long 

 axes of the branches, the sterigmata, and the conidia borne on them 

 stand out from the main axis like rays of a partly opened fan. In 

 Sclerospora philippinensis, on the contrary, the conidiophore top is more 

 compact and less spreading, the axes of branches, sterigmata, and 

 conidia being all approximately parallel to each other and to the main 

 axis. 



These differences in the conidiophores of the two fungi are, on the 

 whole, relative rather than absolute and are influenced to some extent 

 by such environmental conditions as the depth and persistence of the 

 layer of dew in which they develop. Even these distinctions, however, 

 could be used as more absolute and less relative criteria if a very large 

 number of measurements of all parts of the conidiophores were made 

 and assembled to give an adequate quantitative impression. Even 

 from the qualitative rather than quantitative point of view, moreover, 

 these differences, although relative, are constant and distinct, and it 

 should be emphasized that they persist when the two fungi, developing 

 under exactly parallel circumstances on sister plants of the same age, 

 grown side by side under as nearly the same conditions of temperature, 

 soil, dew deposition, etc., as it was possible to obtain, were compared 

 by nightly examinations for several weeks. 



Conidia. — Among the Peronosporaceae as a whole the characteristics 

 of the conidia have been found to be the most valuable basis for dis- 

 tinguishing species. This applies equally well to these two Sclerosporas, 

 since their conidia not only differ markedly and constantly in shape and 

 size but also remain relatively unaffected by changes in environment 

 and hosts. 



In shape, the conidia of the Visayan Sclerospora are at once distin- 

 guished from those of Sclerospora philippinensis. They are not only 

 much more elongate but much more slender as well, the length being 

 frequently two or even three times the diameter. Consequently they 

 range from very elongate ovoid and obovoidal bodies to long narrow, 

 round-ended cylinders, but they are most commonly very elongately 

 ellipsoid in shape. A clearer idea of these variations may be gained 

 from Plate 79, I, J, K. 



In such features as the rounded apex devoid of any papilla, the blunt 

 base with its apiculus of attachment, the hyaline, granular content, 

 and the thin wall, the conidia correspond to those of Sclerospora 



