PERONOSPORA LES 



213 



The whole head may be sterile and abnormally green, i.e., 

 virescent. (Stevens, 1902; Butler, 1907; Kulkarni, 1913; Wilson, 

 1907 6; Weston and Weber, 1928; Melhus, Van Haltern, and 

 Bliss, 1928, Weston, 1929 a, h, c.) 



In 1921 S. macroi^pora Sacc. long known in Europe, was found 

 on wheat in Kentucky and Tennessee (Weston, 1921 b). It has 

 been reported also on Bronius covinmtatus in America and on 

 various hosts abroad. Its life history is poorly understood. 



Fig. 75.- — (a) Sclerospora spontanea Weston, (b-e) S. graniinicola (Sivco.) 

 Schrot. (J-o) S. philippinensia Weston, (o) Sporangiophore. (6) Sporansio- 

 phores emerging from stomate. (c) Young sporangiophore. {d) Sporangiophore 

 hearing sporangia, (e) Oogonium containing oospore. (/) Intercellular myce- 

 lium with haustoria. {g) Germinating sporangium, (e, after A. Fischer; others 

 after Weston.) 



Two species common in the Philippines on maize, S. philippin- 

 ensis Weston and S. spontanea Weston, have been studied 

 critically by Weston (1920; 1921 a; 1923 a, h). In these forms 

 the sporangiophore is more slender than in S. graniinicola and 

 the sporangia much more elongated. The species are character- 

 ized by abundance of sporangia and absence of oospores, the 

 reverse of the situation in S. graminicola. The sporangia ger- 

 minate, moreover, by germ tubes instead of by swarmspores as in 

 that species. In this they resemble several other Oriental 



