Minnesota Plant Diseases. 123 



Allies of green and blue molds. There are numerous allies 

 of these molds which have strange habits indeed. Some, as in 

 the loose-weft fungi, live on feathers and some live on the 

 horns and hoofs of cattle. These fungi are of comparatively 

 rare occurrence and have not yet been collected in Minnesota. 

 Others, however, which resemble the powdery mildews in many 

 respects, are found on the leaves and twigs of living plants, 

 though seldom assuming a destructive parasitic habit. 



False truffles (Tcrfcziacea). As is well known, the truffles 

 are underground bodies resembling, to a small degree at least, 

 small potatoes in appearance. Now the false truffles are very 

 similar to the true truffles in appearance but they differ in some 

 characters. The spore-sacs are not arranged with the same 

 regularity which is common in the true truffles but are found 

 in a loose weft as those in the loose-weft or blue-mold fungi. 

 They may, in fact, be considered as huge underground spore- 

 sac capsules of blue-mold-like fungi. Some of these false truf- 

 fles are apparently the producers of fungus root-hairs in some 

 flowering plants. They have not yet been collected in Minne- 

 sota. 



Black fungi (Pyrcnomycetinca'). These fungi constitute an 

 enormous group of plants. They all agree in having a spore- 

 sac capsule in which the spore-sacs are arranged in definite or- 

 der and arise from the bottom of the capsule. The latter are 

 usually, but not always, black in color and often resemble burnt 

 wood. The spore-capsule in all. except the powdery mildews, 

 has a definite method of opening by means of a pore which is 

 sometimes protected by spiny processes. The simplest forms, 

 the powdery mildews, are very similar in many respects to the 

 blue and green mold plants and are their nearest relatives. 

 Like these molds the black fungi possess accessory spore-forms 

 and those of the powdery mildews, constituting the summer 

 spores, are particularly like the green mold spores of the green 

 mold fungi. They are not. however, green in color. The 

 black fungi are conspicuous in the great number and variety 

 of accessory spore-forms. Some species alone possess three or 

 four kinds of such spores in addition to the sac-spores. The 

 common Minnesota forms of the vast number of plants in this 

 group can be arranged in the following ten groups. 



