394 Minnesota Plant Diseases. 



form a protective coat to the inner cells, which are the func- 

 tional spores. 



Diseased plants should be removed and burned. 



Smut of pigeon grass (Ustilago ncglecta Niessl.). There 

 are several smuts which attack the common pigeon grass. 

 Commonly the grains are replaced by the smut-spore-mass, 

 which is at first covered by a thin wall. These closed masses 

 have often a purplish tinge. The spore-mass is black. 



Smut of bromes (Ustilago bromivora Fisch.). See Diseases 

 of Field Crops. 



Root smut of sedge (Schinzia cypericola Magn.). This is 

 an uncommon smut and would not be readily recognized as a 

 member of the smut family. Indeed it is very possible that it 

 does not belong to this group. It is moreover of no economic 

 importance but is of interest on account of its root-inhabiting 

 character, a very rare phenomenon in smuts. It attacks sedge 

 roots forming tuber-like swellings which are often branched in 

 finger fashion. The spores are produced internally on the ends 

 of short threads of the mycelium. This smut occurs in Minne- 

 sota, though very rarely. 



Honey dew fungi (Apiosporium, Capnodium and other re- 

 lated genera). These fungi constitute a group of plants with 

 peculiar habits, which have already been partially explained. 

 They belong to the burnt-wood fungi, producing a mycelium of 

 charcoal-like texture and fruiting bodies of the same nature. 

 They are not true parasites, but are saprophytes, which prefer 

 to live on the excreta of various insects. As these excreta are 

 found largely on living leaves the fungus mycelium comes to 

 spread over the surface of the leaf and often to completely en- 

 close it in a dark mycelium. This position may slightly inter- 

 fere with the light, though the leaf is seldom injured in conse- 

 quence. These fungi do not effect any important losses to agri- 

 cultural plants in Minnesota though a number of them are 

 found in the state. 



Mold of honey-colored mushroom [Endomyces decipiens 

 (Tul.) Reess.]. One sometimes finds upon the "mushrooms" of 

 the honey agaric (Agaricus melleus), which is so common in 

 Minnesota in late autumn, a mold-like parasite. The mycelium 

 threads of the parasite permeate the tissues of the mushroom. 



