414 



General Botany 



Fig. 255. A group of lichens : Parmelia {on tree) ; in the middle foreground, P£;///|:6'm; 

 the renaaining forms are species of Cladonia. 



Lichens also multiply vegetatively by the breaking away of small 

 bits of the thalli. 



BASIDIUM FUNGI OR BASIDIOMYCETES 



The second largest division of the fungi includes the smuts, 

 rusts, and toadstools, numbering more than 20,000 species. 

 The distinctive feature of the Basidiomycetes is the formation of 

 one, two, or four spores at the end of a short, club-shaped hypha 

 called a basidium. In the smuts and rusts the basidium and 

 basidiospores make up a separate plant ; in the toadstools the 

 basidium and its spores are formed on or in the fleshy fruiting 

 body of the fungus. 



The smuts. The smut fungi of the small cereals have a myce- 

 lium extending throughout the tissues of the host plant, which was 

 infected during its seedling stage. When the plant " heads out," 

 the smut causes the grains to enlarge, and the smut hyphae con- 

 sume the food usually stored in the grain and then produce 

 black spores in such abundance as completely to occupy or 

 replace the grain. These spores have heavy walls and are capable 

 of living over to the next season. In some cases this involves 



