284 



USTILAGINEAE. 



formation of conidia ensues ; the conidia multiply in a yeast- 

 like manner, and only grow out as hyphae on exhaustion of 

 nutritive material. Infection takes place on seedling-plants. 



Kiiliu cultivated this species on Sorghum saccharatum and S. vulgare, 

 and suggests that a common disease of Durra in South Africa may be 

 caused by this parasite. 



Ust. sorghi (Link.) (Ust. Tulasnei Kiihn) (U.S. America). 

 This is another widely distributed parasite of Sorghum vulgare 

 and S. saccharatum. Its external appearance is described by 

 Kiihn somewhat as follows : " Diseased plants attain to almost 

 their normal size, and the flower-head is developed as far as 

 the glumes. The ovary, however, is completely metamorphosed 

 into a sac filled with spores, its outer wall forming a delicate 



FIG. 154- Ustilago cruenta. Spikelet 

 enlarged from a head of Sore/hum. The 

 ovaries are transformed into long flask- 

 shaped sacs, from slits of which the 

 spores are emerging as a black powder. 

 4 natural size. (v. Tubeuf del.) 



FIG. 155. Ustilago cruenta. Germin- 

 ating and sprouting conidia from a 

 cultivation in plum-gelatine, (v. Tubeuf 

 del.) 



whitish coat, which is easily torn, and, when the spores have 

 escaped, a columella will be found to occupy the centre of the 

 smut-niass. The stamens may also become filled with spores, 

 and be externally more or less irrecognizable. As a rule, all the 

 flowers of a head are smutty; if any escape, they remain more 

 or less rudimentary." 



The spores, according to Brefeld, germinate only in nutritive 

 solutions. They produce a four-celled promycelium, on which 

 few conidia are formed. 



Ust. sacchari liabh. Dust-brand of cane sugar. This fungus 

 injures the stems and head's of Saccharum officinalc, S. cylindrieum, 

 and S. Erianilii in Italy, Africa, and Java. 



Ust. sacchari-ciliaris Bref. occurs on Saccharum ciliare near 

 Calcutta. 



Ust. avenae (1'ers.). The smut or brand of the oat occurs 



