ASCOMYCETES 



247 



originates, and the asci to which it gives rise obtain room for com- 

 plete development either by forcing the separation of the cells in 

 the center of the cellular body or by dissolving some of these. The 

 mature perithecium consists of a flask-shaped structure, the mouth 

 of which projects, along with the tissues which inclose it, slightly 

 beyond the general level (Fig. 106, b). Within the neck of this 

 perithecium are to be found many periphy- 

 ses. The mature asci are long-clavate. Each 

 ascus contains eight filiform spores, averaging 

 6070 /A in length, which issue from the tip 

 of the ascus and readily germinate in water 

 (Fig. 1 06, c). 



Control. Proper precautions in the selec- 

 tion of the grain seed, together with thorough 

 preparation of the land, obviate any danger in 

 the case of rye. When detected in the har- 

 vested product, the sclerotia must be shaken 

 out or the product discarded. When ergot 

 appears in abundance on grasses in the pas- 

 ture, either the animals must be taken off 

 until the ergot falls, or, where possible, the 

 grass may be mowed with a machine the blade 

 of which may be set high. In the latter case 

 subsequent raking may be unnecessary. In 

 the central West, ergot is not uncommon on 

 the chief pasture crop, blue grass (Poa pratensis}. This may not 

 be ergot of rye, for besides that species, two ergot-producing fungi 

 have been reported on Poa, Claviceps microcephala (Wallr.) Tul. 

 and Claviceps setulosa (Quel.) Sacc. 1 



1 A disease of rice known as green smut is well developed in the rice-growing 

 regions of Japan and Louisiana. The effect of the fungus is conspicuous (Fig. 107), 

 although only a few grains in a head are affected. The disease has every appear- 

 ance externally of being a smut. Brefeld (Unters. a. d. Gesammtg. d. Myk. 12 : 

 194) and others have studied this form. Brefeld has studied also more particularly 

 a related species on Setaria crus-ardea. In both cases the smut-like body is a 

 typical sclerotium surrounded by looser hyphae and the dark walled spores. Germi- 

 nation studies of the spores seem to indicate that they are conidia, and it has 

 been suggested that the fungus may prove to be an ascomycetous form, possibly 

 one of the Hypocreales. The species on rice bears the name Ustilaginoidea Oryzce 

 (Cke.) Tak. 



FIG. 107. USTILAGINOI- 

 DEA ON RICE. (Photo- 

 graph by H. R. Fulton) 



