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beris vulgaris) they send tubes into the young tissues, usually the leaves, 

 and the mycelium develops there. In about a week small dot-like yel- 

 lowish swellings are seen on the leaf. These are the spermagonia, flask- 

 shaped cases which produce a large number of small spores called sper- 

 matia. As far as is known these have no function whatever. A few 

 days later on the under side of the leaves, cup-shaped or cylindrical struc- 

 tures arise which contain a large number of spores in chains. These spores 

 are yellow in colour. They are soon shed but will not attack the barberry 

 leaves. If they are carried to grains in suitable grasses, however, they send 

 tubes through the breathing pores into the tissues of the host. The myce- 

 lium develops rapidly among the tissues and in about ten days yellow 

 masses of stalked spores, the uredospores, are produced on this mycelium. 

 They break through the epidermis and appear as linear masses of loose 

 spores which are easily carried by the wind and spread the fungus on 

 grain during the summer. Later from the same mycelium masses of dark 

 thick walled, two celled spores arise, the teleutospores. They rupture 

 the epidermis and appear as dark compact linear masses which give the 

 black appearance to the stems of the rusted grain. These spores will 

 only germinate if exposed to the weather during the winter. When the 

 warm spring weather comes they produce secondary spores, the sporidia, 

 which will not infect grains as far as is known, but will attack the com- 

 mon barberry. The statement made in some texts that sporidia will 

 infect grains has no evidence whatever to support it. 



It is well knowMi, however, that the stem rust persists and is abun- 

 dant even in countries where the barberry does not grow, so there must 

 be some other way in which the stem rust is carried over the winter. The 

 uredospores are known to live through severe winters in the Northern 

 United States, and the writer has found a very small percentage to survive 

 Quebec winters. So it is probable that the uredospore is able to carry 

 the fungus over the winter. The uredospores persist during the winter 

 in the Southern United States and some of the spring infection may come 

 from spores blown northward by the wind. It is also possible that the 

 fungus survives the winter in the form of mycelium in grasses, and when 

 spores are produced in the spring they may infect grains. However, 

 it has been found that rusts do not pass readily from many grasses to 

 grains. 



It was formerly thought that the stem rust of grains (Puccinia 

 graminis) was a single species passing readily from one kind of grain or 

 grass to another, but infection experiments carried on in Europe and 

 the United States have shown that though the spores in the different 

 grains are alike in appearance yet there is a difference in infecting power. 



