306 Minnesota Plant Diseases. 



are borne on the ends of beaded threads and are two-celled. The 

 spore-sac capsules are borne in a blackish cake of mycelium, 

 somewhat similar in appearance to the tar-spot of willows. The 

 fungus is also known on the scarlet clover (Trifolium incarna- 

 tum). It is sometimes known as the black mold of clover. 



Smothering fungus of grasses [Epichloe typhina (P.) Tnl.]. 

 This disease is also known as the Reed Mace Fungus. It is found 

 on grasses and is apparently confined to a few genera. It some- 

 times causes injury to fodder grasses. The fungus attacks the 

 above-ground portion o<f the grass and forms white or light tan- 

 colored cushions of mycelium around the leaves and stem of the 

 host. These cushions are so dense that they prevent further 

 growth of the leaves and stem, causing, as it were, strangulation. 

 From this cushion arise first, small colorless spores on short 

 stalks. These are the summer spores, comparable to those of 

 the powdery mildews. Toward fall the sac-spore-capsules are 

 developed. They arise in great numbers, embedded in the outer 

 part of the cushion and are of the same color as the cushion. 

 They are long and pear-shaped, and open to the surface by 

 means of a pore at the end of a slightly protruding neck. In 

 each capsule a large number of sacs are produced in a group, 

 on the floor of the capsule cavity, and each sac contains eight 

 spores. The spores are very long and thread-like and are di- 

 vided into many cells, arranged in a chain. When ripe, the 

 spores may break up into segments, each of which is capable 

 of germination, producing a mycelium and causing infection. 

 The fungus, when occurring in great abundance on fodder 

 grasses, is said to be injurious to the feeding horses. It sel- 

 dom becomes a serious pest. (See Figs. 57 and 58.) 



The ergot disease of grasses \Claviceps purpurea (Fr.) Tnl. 

 and other species}. The ergots of grasses are very closely related 

 to the smothering fungus of the same plants. The ergot fun- 

 gus attacks the very young and immature grains and the my- 

 celium soon permeates the tissues of the grain. It replaces the 

 latter entirely and forms in its stead a dense mycelium which 

 soon becomes so densely interwoven that it forms a solid body 

 of characteristic form and of doughy consistency. The outer 

 surface of this body is at first thrown into folds and ridges and 

 along these folds one finds the summer spores produced in 



