CLASSIFICATION OF FUNGI 63 



T. foetans, (B. & C.) Trel., commonly known as 

 the bunt or stinking smut of wheat. It is widely dis- 

 tributed throughout the wheat-growing countries. The 

 spores are produced almost entirely within the grain, 

 and are distributed and sown with the seed. They 

 germinate, producing the promycelium on which are 

 produced the sporidia, and the infection takes place 

 through the young plants. 



The Protobasidimycetes contains the order Uredinales 

 or rusts. This order contains a greater number of 

 parasites than any other order, many of which attack 

 agricultural crops. The rusts are also very interesting 

 because of their peculiar habits in attacking different 

 hosts. These fungi have three stages, the aecidiospores 

 or spring spores, the uredo or summer spores, and the 

 teleuto or winter spores. In the spring, yellow spots 

 occur on the leaves, and in a short time burst open, 

 exposing great masses of spores which are borne in 

 chains. These are the aecidiospores, which are carried 

 to the proper host and in a short time produce mycelia 

 which penetrate its tissues. The next is the uredospore 

 stage of which there may be several generations. The 

 uredospores are borne singly on the ends of aerial hyphae. 

 The third generation is the teleutospore stage, which is 

 the resting stage. In due time these spores germinate 

 and produce sporidia, which in turn produce mycelium, 

 again starting the life cycle of the fungus. In many 

 species these stages occur on host plants from two 

 entirely different orders, usually the aecidia upon one, 

 and the other two stages upon another ; or in some 

 cases the fungus produces only two stages, each upon a 

 different host ; while other species are confined to a 

 single host. Some are without aecidial stage, others 

 without uredo stage, while still others are without the 

 teleutospore stage. 



The rusts are among the most important fungi that 

 cause disease. While they do not as a rule completely 

 destroy the plant, they reduce its vigour and cause a 

 decrease in the yield. Hemileia vastatrix, Berk, and Br. 



