BASIDIA-BEARING FUNGI (SMUTS) l8l 



Experiments to determine the vitality of smut spores have shown 

 that those of the stinking smut of wheat, covered smut of barley and 

 oat smut are long-Hved under favorable conditions for seven, or eight 

 years, and in a dry condition are resistant to frost. Where vegetative 

 reproduction occurs, as in the loose smuts, the spores lose their vitality 

 after five to six months. It has also been determined that stinking 

 smut spores passing through the bodies of animals lose their power of 

 germination in a great majority of cases. Only those passing through 

 pigs retain their vitaHty a longer time. The presence of occasional 

 viable spores in the manurial offal of animals suggests a danger of 

 the spreading of smut diseases through manure applied to fields as 

 fertihzers. 



Germination (Fig. 62). — The spores, when placed in a drop of 

 water, send out a single hyaline thread several times the length of 

 the spore, and this thread, or promycelium, becomes divided into four 

 cells by cross-partitions, or septas. Usually the apex of these four cells 

 produce one or more elongated thin-walled spores, the basidiospores, 

 or sporidea. These basidiospores are pinched ofif at the base, and 

 others are formed to take their place. When the basidiospores reach 

 the proper host, whether in the seed, seedling, partly grown or mature 

 condition, it forms on germination an infection hypha, which bores 

 through the surface and enters the interior of the host. Once inside a 

 mycelium is formed. 



Modes of Infection. — (i) Certain smut spores, as those of the 

 stinking smut of wheat, covered smut of barley, naked and loose smuts 

 of oats and others, adhere to the outside of the grains and are sown 

 along with the grain. In the soil germination takes place and the spore 

 produces a short stout mycelium, which develops secondary, or even 

 tertiary spores, which by means of infection threads attack the young 

 grain seedlings as they grow upward through the soil. This mode of 

 infection is called seedling infection. (2) In the so-called loose smuts 

 of wheat and barley, the chlamydospores, which are mature at the time 

 of flowering of these commercial grasses, fall upon the female organs 

 of the wheat, or barley, and germinating the infection hypha pushes 

 its way into the developing grain where it remains dormant as a deli- 

 cate mycelium. The normal development of the grain is not inhibited, 

 so that when it is planted as seed, the mycelium begins to grow with 

 the seedling and keeps pace with the future growth of its host until 



