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A TEXTBOOK OF THEORETICAL BOTANY 



Actually five species of Ustilago are involved in attacking the three species 

 of cereals mentioned, for Oats and Barley have both Loose and Covered 

 Smuts, while Wheat is only attacked by a Loose Smut. The following 

 table will make this clear : — 



So far as the spores are concerned there is little difference between them, 

 but the species will only attack their own host plant, and the Loose Smut 

 type will not produce the Covered Smut appearance or vice versa. On the 

 other hand, artificial hybrids have been produced between the various 

 spore types. 



Life-history of the Fungus 



The spores produced either in the flowers or in the grain are variously 

 referred to as simply spores, brand spores or chlamydospores (Fig. 302). 







•^ i^***w 



Fig. 302. — Ustilago avetiae. Chlamydospores 

 in the ovarv of Arena. 



They are black in colour and each spore has a fairly thick wall, which is 

 slightly echinulate except in U. levis which is smooth. In the presence of 

 warmth and moisture they germinate in about a day. The wall splits open 

 and a short colourless hypha grows out. The nucleus of the spore divides 



