54 FUNGOID DISEASES 



By inoculation experiments Klebahn has shown 

 that there are two distinct species, viz. : — 



(i) Puccinia coronata — found on many grasses, 

 especially Dadylis glomerata (cocksfoot) 

 and Festuca silvatica, a variety of sheep's 

 fescue, 

 (ii) Puccinia coronifera — which occurs on 

 various grasses, and also on oats, but not 

 on wheat and barley. 

 The uredospores of P. coronifera are found on 

 the upper surface of the leaf of oat plants, in the 

 form of small orange coloured sori. The teleuto- 

 spores are in the form of minute greyish black spots, 

 and are characterized by a crown of spines around 

 the end cell ; hence the name ''crown rust" (see 

 Fig. 14, F). Apparendy they are not able to ger- 

 minate until the spring. 



The aicidiospores are found on the buck- 

 thorn. 



Preventive Measures. — Owing to the di\'ersity of 

 spore formation, and to the mycelium being within 

 the plant, the various rust diseases are most difficult 

 to combat. Spraying and pickling of the grain 

 are quite out of the question, hence any recom- 

 mendations must of necessity be of a general 

 character. 



1 . Avoid heavy dressings of nitrate of soda, give 

 small amounts along with superphosphate. 



2. Select varieties which show least susceptibility 



