USTILAGO. 



283 



the pustules are fewer in number the parts of the ear retain 

 their normal position, but all the floral organs contained in 

 the glumes are wholly or partially converted into irregular 

 greyish smut- masses. Isolated pustules may occur under the 

 inflorescence, on the next internode of the haulm." 



Fig. 153. — UstUago cruenta. Smut of Durra or Sorghum. The head has been 

 divided up and the isolated branches photographed. The ovaries are transformed 

 to long crooked sacs, and pustule-like outgrowths are also present on stalklets and 

 stalks, (v. Tubeuf phot, from material supplied by Prof. Dr. Jul. RUhn.) 



The spores are yellow to brown in colour, smooth-walled, 

 and of very variable shape, 5-12/it long and 5-9/« broad. As 

 a rule, germination in water results in the formation of a germ- 

 tube composed of four or five cells, which elongate to long 

 mycelial threads or, exceptionally, produce a single conidium. 

 As a result of germination in nutritive solutions, a lively 



