117 



allowed to mature after being inoculated, thirty were planted in a box in 

 the greenhouse on October 10th, 1907. On the 15th of May, 1908, the re- 

 sulting wheat-plants had begun to head out. All the heads were more or 

 less smutty. The majority of them were reduced to a mass of spores as 

 is commonly observed in the field. In a few cases the ovary was the only 

 part entirely destroyed, the outer portion being unaffected or only streaked 

 with sori containing the spores. As the wheat plant develops the mycelium 

 of the fungus grows upward probably much after the manner of the my- 

 celium of the stinking smut. It enters the young head early in its forma- 

 tion and branches into numerous sporogenous hyphae, which completely 

 destroy the pistil and other parts of the flower. These hyphae divide into 

 a number of cells within each of which a chlamydospore is formed as in 

 Oat Smut. The walls of the hyphae become gelatinous and later disap- 

 pear, leaving the spores free. These dry on exposure to the air, forming 

 a dusty mass so commonly observed at the flowering time of wheat. These 

 spores are blown about by the wind and infect the ovaries of healthy 

 heads, thus establishing the fungus for another year. (Fig. 6.) 



Naked Smut of Barley. 

 Ustilago nuda (Jens.) Kell. and Sw. on Hordeum vulgare. 

 This Smut is similar in methods of attack and in field characteristics 

 to the Loose Smut of wheat. The head is reduced to a mass of spores 

 which are scattered at the flowering time of barley. These spores infect 

 the ovaries of the healthy plants in which the mycelium of the fungus 

 develops until the seed is ripe, remaining throughout the winter in a dor- 

 mant condition and continuing its growth concurrently with the growth 

 of wheat after seed is planted. 



The Stinking Smut of Wheat. 



Tilletia foetens (B., & C.) Trelease and T. Tritici (Bjerk.) Wint. on Triti- 



cum vulgare. 



Tilletia foetens has a spore with a perfectly smooth coat, while the 

 epispore of T. tritici is much reticulated. Their method of infection and 

 growth are similar. 



The spores of these two smuts are scattered about at harvesting time 

 or in some other way become attached to the healthy seed. When placed 

 in a situation favorable for their germination they send out a short, thick 

 promycelium and at its tip is borne a cluster of slender tapering sporidia 



[9—21363] 



