190 



MYCOLOGY 



upright and divided transversely into four cells, each of which cuts off 

 abasidiospore. These basidiospores are blown to the leaves, twigs, or 

 fruits of the barberry where a mycelium is formed. Later pycnia 

 (spermogonia) appear on the upper side of its leaf. These are accom- 

 panied by round, fringed depressions, the cluster cups or aecia, which 

 appear in the spring on the lower side of the leaves. The aeciospores 

 are arranged in chains. These spring spores, asciospores, are carried to 

 the wheat plant where they induce the characteristic rusted appearance 



basidium 



teleutospore 



basidiospore 



uredospore m 



O 



uredospore 



mycelium 

 secidiospi 



fusion-cell 



Fig. 65. — Relations of various spore forms of rusts to each other. (After Grove, W. 

 B., The British Rust Fungi, 1913, 40.) 



of the cereal. The wheat plant is not killed by the attack of the fungus 

 which, however, prevents the reserve foods from being properly stored 

 in the grains; hence, they are mushy and unfit for storage, or for bread- 

 making purposes. It has been recently shown that in Australia and the 

 plains of India, where the barberry is unknown, the black rust of wheat 

 does serious danjage. Three methods are open to the wheat rust to 

 winter over: (i) The fungus may winter by its urediniospores, (2) by a 

 perennial mycelium, (3) by Eriksson's mycoplasm. Arthur, in Amer? 

 ica, and others have shown that it winters by its urediniospores, or 



