CROWN" RUST OF OATS. 45 



the nijitter it is impossible to deteruiiue whether this rust or the leaf 

 rust of wheat is referred to. 



The economical bearing of this subject is most important. A fact of 

 much significance is that the leaf rusts of wheat and rye are the only- 

 cereal rusts that winter their uredos in this country and are at the 

 same time the only ones that can not be transferred by inoculations to 

 any other host except species of the same genera. The obvious infer- 

 ence is that these rusts per|)etuate themselves from year to year prin- 

 cipally by means of their uredos, but that occasionally the teleutospores 

 probably bridge over unusually severe winters, either by means of 

 some a^cidium as yet unsuspected or by direct infection of the young 

 plant early in the spring through the germinating sporidia. There is 

 still the possibility, however, that other nredo hosts may be found. 

 Of course if these three alternatives were absent these rusts could be 

 readily eradicated by the concerted action of farmers in keeping their 

 farms rigidly clean of volunteer grain. 



Liability of different varieties to this rust. — On account of so few 

 sorts of rye being grown in this country, no particular attention has 

 been given to the subject of rust liability of varieties. However, it 

 may be said that all fields of rye, without exception, are usually more 

 or less afi'ected. 



In the experiments at Salina a number of packages of spring rye 

 ("yaritsa" in Russian), received from the region near Nerchinsk, Siberia, 

 were tested, some of them being planted in the autumn and some in 

 the spring. All the plants were rusted, the rustiness ranging from GO 

 to 80 per cent. 



Damage. — The damage to rye from this rust is very little, as a rule, 

 as in the case of leaf rust of wheat. According to Humphrey (40, pp. 

 228, 229) and Thaxter (67, p. 98), it occasionally causes considerable 

 injury in Massachusetts and Connecticut, and it is also said to be quite 

 injurious at times in the Southern States. According to Prof. J. H. 

 Connell, director of the Agricultural Experiment Station, College Sta- 

 tion, Tex., rye in the experimental plats of the station is occasionally 

 injured by this rust even in January. 



CROWN RUST OF OATS. 

 {Puccinia coronata Corda.) 



Physiological relations. — The fact that this rust occurs on oats only, 

 and that its appearance, both superficially and microscopically, is very 

 different from that of the black stem rust, together with the peculiar 

 form of its teleutospores, make it the most distinct of all the cereal 

 rusts. The uredospores are so much like those of the leaf rusts of 

 wheat and rye, however, that when only these were i)resent the writer 

 could not be certain that the crown rust and the leaf rusts did not 

 exchange hosts until he determined the matter by inoculation. There 



