~ THE RUSTS OF NOVA SCOTIA. FRASER. 385 



infection takes place. Many grasses are attacked by this rust, 

 arid some observers have thought that the mycelium may 

 survive the winter in these grasses, and that infection of the 

 grain crops may come from this source in the spring when 

 uredospores are produced. However, artificial infection experi- 

 ments indicate that few of the grass rusts will grow on wheat 

 or other grains. The rusts on the various species have become 

 adapted to their particular host and will not usually grow on 

 other species. 



Little can be done to combat this rust. Varieties that ripen 

 early are not usually so badly affected, so early sowing and the 

 sowing of early varieties would be advantageous. Some varieties 

 are more susceptible than others and attention is now being- 

 given by plant breeders to the production of rust proof varieties. 

 It is probable that much may yet be accomplished along this 

 line. The barberry which is sometimes grown in hedges should 

 be destroyed as it probably forma a bridging host between the 

 various specialized forms on the grasses. 



The crown rust of oats (Puccinia Lolii} is very common on 

 the oat about Pictou and must do much injury to the crop. It 

 is found only on the oat and can be easily distinguished from 

 the stem rust, as the telia remain covered by the epidermis ani 

 occur only on the loaves and sheaths. The aecial stage is found 

 on the buckthorn, an introduced tree or shrub which is rather 

 common along some roadsides near Pictou. This may account 

 for the prevalence of the rust as these trees showed a rather 

 pronounced infection in the springs of 1909-10. !N"o control 

 measures are known, but the destruction of the aecial host. 



The brown or covered rust of wheat, Puccinia triticina, is 

 quite common about Pictou. The telia are usually formed 

 on the lower side of the leaves. They are black in color and 

 remain covered by the epidermis. This rust usually passes in 

 America under the name Puccinia rubigo-vera or P. rubigo- 

 rero iritici Its systematic position is somewhat unsettled, and 

 its aecial stai^e somewhat doubtful. 



