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. 



Kiihn 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 



Pig. 154. — Ustilago cruenta. Spikelet 

 enlarged from a bead of Sorghum. The 

 ovaries are transformed into long flask- 

 shaped sacs, from slits of which the 

 spores are emerging as a black powder. 

 ^ natural size. (v. Tubeuf del.) 



Pig. 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 liave 

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

 smut-mass. 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 Eabh. Dust-brand of cane sugar. This fungus 

 injures the stems and heads of Saccharum officinale, S. cylindricum, 

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



Ust. sacchari-ciliaris Bref occurs on Saccharum ciliare near 

 Calcutta. 



Ust. avenae (Pers.). The smut or brand of the oat occurs 



