394 



THALLOPHYTES 



study of the formation of these spores shows that they are not 

 basidiospores, for they are not formed on basidia. The hyphae 

 in the smut ball simply divide into cells which separate and 

 become spores. These spores are the so-called brand spores, the 

 whole mass of them forming the so-called Smut. The spores are 

 very heavy-walled and appear black in mass. This kind of a 

 heavy-walled spore, which is simply a transformed vegetative 

 cell of the mycelium, is called a chlamydospore, a name referring 

 to the heavy protective wall. The spore masses break up when 

 mature and the spores are shed. In han- 

 dling the grain, especially in thrashing, the 

 spores escape in dust-like fogs. The spores 

 pass the winter on the ground, straw, grain, 

 or wherever they happen to fall. Many 

 of the spores lodge on the Oat grain, fall- 

 ing down between the lemma and palea 

 which enclose the Oat kernel. The follow- 

 ing spring the chlamydospores germinate, 

 each producing a small hypha called a pro- 

 mycelium, on which the basidiospores are pro- 

 duced. The basidiospores are produced on 

 the end and sides of the promycelium as 

 shown in Figure 351. Their number is in- 

 definite and they often multiply by budding 

 after the manner of the Yeasts. They are 

 quite commonly called conidia and often 

 sporidia, although they are comparable to the 

 basidiospores cf the Toadstools and Puff- 

 balls. It is on account of the occurrence of 

 the promycelium, which is regarded as a 

 basidium, that the Smuts are classed as Basidiomycetes. Once 

 in contact with a young Oat plant, the basidiospores produce 

 hyphae, known as infection hyphae, which penetrate the young 

 plant and start the development of a mycelium. 



It has been found that most of the infection in Oat Smut 

 results from the chlamydospores which are lodged on the grain, 

 and that by soaking s.eed Oats in hot water (132° to 133° F.) for 

 ten to fifteen minutes or in water containing about 1 pint of 

 40 per cent formalin to 45 gallons of water, the spores can be 

 killed and much loss to the Oat crop prevented. 



Fig. 351. — Ger- 

 mination of Chlamy- 

 dospores. At the 

 left, a spore, and at 

 the right, a spore 

 which has germinated 

 and produced a pro- 

 mycelium bearing 

 basidiospores (c). X 

 about 300. 



