SMUTS 237 



much crowding and distortion of these soft-walled spore- 

 bearing filaments, but here and there this structure may 

 be made out. When the spores are ripe, the gelatinous 

 walls dissolve and, the watery portions evaporating, 

 leave a dusty mass of black spores. The spores germinate 

 by sending out a short septate filament (promycelium) 

 upon which minute sporids are formed laterally, much 

 as in the Wheat rust. Like other smuts, that of Com 

 is capable of growing as a saprophyte in the decaying 

 vegetable matter of the soil, producing an abundance of 

 conidia. It has been found that when the sporids or the 

 conidia germinate upon the meristematic parts of the 

 growing plant or the projecting styles of the developing 

 ears they penetrate the surface layers, and thus secure 

 admission to the tissues of their host. 



408. Other Smuts, as Wheat smut or Black Blast 

 (Ustilago tritid) of wheat, Oat smut {U. avenae), Barley 

 smut (C/. hordei), etc., have a structure and mode of devel- 

 opment closely resembling the foregoing, but with most of 

 these the hosts can be infected only when very young, i.e. 

 during or shortly after germination, or through their 

 stigmas at the time of flowering. 



409. The Bunt or Stinking smut of wheat {Tilletia 

 tritid and T. foetens) represent an allied family {Tille- 

 tiaceae) in which the sporids are formed in a whorl at the 

 end of the non-septate promycelium. 



Laboratory Studies, (a) Collect specimens of cluster cups 

 (from barberry, buttercups, or evening primroses, etc.); ex- 

 amine first under a low power without making sections. Note 

 the cups filled with yellowish or orange conidia (aeciospores). 

 Note spermogones (minute dark spots) generally on the opposite 

 side of the leaf. 



(6) Make very thin cross-sections through a mass of cups so 

 as to obtain vertical sections of the cups and the spermogones. 



(c) In May, June or July collect leaves of wheat, oats, or 



