USTILAGO. 291 



The spores are smooth-coated and spherical or elHptical, 9-1 2 /x 

 long, and 8-10 fx broad. According to Brefeld, they germinate 

 in two or three days in water, and produce proraycelia with four 

 or five cells ; the cells may either bud out directly and become 

 hyphae, or do so after previous fusion. 



Spores placed in nutritive solutions germinate in about three 

 days, and produce several strong septate promycelia with spindle- 

 shaped conidia. The conidia as a rule germinate directly into 

 branching hyphae ; fusion of conidia is not known, and secondary 

 conidia are only rarely formed. The hyphae become septate 

 in their older parts, and produce conidia in two ways, firstly, 

 from hyphae in the solution itself; secondly, from aerial hyphal 

 branches which rise out of the solution and give off conidia 

 in a manner similar to mould-fungi. 



Brefeld states that infection takes place by means of the 

 germinating conidia. Only resting-spores are produced on the 

 plant itself, and these retain their capacity for germination 

 for years. 



Ust. Rabenhorstiana Kiihn^ (U.S. America). This is found 

 on Panicum miliaccum, P. glabrum, P. linearc, and P. sanguinale. 

 It destroys flowers, ears, and upper part of haulms. The spores 

 are brown and spiny ; they germinate, but do not produce 

 conidia. 



Ust. sphaerogena Burrill. An American species causing 

 distortion of the spikelets of Panicum Crus-galli. The malforma- 

 tions resemble those produced on the same host by Tohjposporium 

 hullatum, but differ in having a rough surface with short rigid 

 hairs. The spores are free and germinate easily in water, 

 producing promycelia which give off conidia. The conidia 

 frequently sprout for a time in a yeast-like manner. 



The following are American species : 

 Ust. diplospora Ell et Ev. On Panicum sanguinale. 

 Ust. trichophora Lk. On Panicum colinum. 



Ust. setariae Eabh. On Panicum sanguinale ; probably identical witli 

 Ust. liabenhorstiana. 



Ust. panici-leucophaei Bref. On Panicum leucophaeum in Rio de Janeiro. 



Ust. digitariae Kze occurs on the flowers of Panicum 

 {Dvjitaria) >>aii(juliialc, P. glahrum, and P. rcpois. The spores 

 are smooth-walled. 



' Kiilni, mibrifjia, 1876. 



