Minnesota Plant Diseases. 309 



capsules with their pore-like openings. The arrangement of 

 the capsules is similar to that in the smothering fungus, except 

 that the cushion is spherical in shape. In the capsules are nu- 

 merous sacs, each containing eight spores. The latter are very 

 long and thread-like and are many times divided by cross walls 

 and each division is capable of the formation of a mycelium. 

 The flowers of the grass plant are again infected by these spore- 

 segments from the sacs. 



The storage-body or sclerotium is widely used medicinally 

 and is known as the ergot of rye. In the grains of the latter it 

 is very commonly found. These ergots sometimes attain a 

 length of one and one-half inches. The presence of ergot 

 amongst grains from which flour is made may give rise, among 

 the consumers of the bread, to a disease known as ergotism. 

 Cattle fed with grains containing ergots in considerable amounts 

 may also be severely poisoned. Numerous cases of such poi- 

 sonings in our northwestern states have been reported. 

 Chronic effects, from long-continued small doses, can be distin- 

 guished from acute attacks. The shape of the sclerotium varies 

 with the grain, upon which it is formed. Ergots grow on many 

 of our very common wild grasses and are sometimes here even 

 more conspicuous than on the cereal grasses. 



The only preventive means for ergot lie in the destruction of 

 all sclerotia and in the planting of clean seeds, i. e., seeds free 

 from an admixture of ergots. 



Leaf spot of alfalfa [Pseiidopeziza medicaginis (Lib.) Sacc.]. 

 This small cup fungus causes yellowish spots upon the leaves. 

 In the center of each spot are seen the tiny black fruiting bod- 

 ies. These are cups of such minute size that they can be clearly 

 seen only with the aid of the hand lens. The disease is some- 

 times serious, and in Iowa has at times caused a loss of one- 

 half of the crop. Frequent cutting keeps down the disease by 

 preventing the maturing of the fruiting bodies and thus pre- 

 venting infection. The spores mature in early summer, proba- 

 bly in June. Diseased plants may be cut when the disease first 

 appears. 



-Cup-fungus leaf-spot of clover {Pseudopeziza trifolii Fckl.). 

 This fungus occasions local epidemics among clover and lu- 

 cerne crops. It is one of the cup fungi but the cup is so minute 



