FUNGI 109 



spores are produced by budding. The basidium is a terminal 

 hypha and is either unicellular and bears the four spores at its 

 free end or else it is divided into four cells each one of which 

 bears one spore. 



Rudimentary sexual organs are found but there is usually no 

 sexual process connected with the formation of spores. The 

 basidia are usually grouped and borne on the surface, or within 

 special fruiting bodies. Besides the basidiospores there may be 

 also one or more other kinds of spores formed by the same 

 fungus. 



253. Order i. — Hemihasidialcs are parasitic on plants. The black 

 corn-smut is a familiar example. A short hypha which is supposed to 

 represent the basidium is developed directly from the thick-walled brand 

 spores. The mycelium developed from the basidiospores ramifies through 

 the tissues of the host and ultimately produces large masses of brand spores. 



254. Order 2. — Protohasidiomycetes have a basidium divided into four 

 cells each of which bears a spore. The "rusts" are the most important 

 members of this group. See p. 364 for the Hfe history of the wheat rust. 

 There are also some saprophytic forms which have a gelatinous thallus. 



255. Order 3.— The Autobasidiomycetes have the basidium undivided 

 but bearing four sterigmata with one basidiospore on each. The group is 

 a very large one. In most cases the basidia are arranged in a well-defined 

 layer called the hymenium and this is borne on a fruiting body of very 

 definite form. The hymenium may form a single flat surface, or it may 

 be variously folded into numerous tooth-like of finger-Hke projections or 

 parallel plates. In other groups again it lines the walls of slender tubes 

 or of numerous closed chambers. To this order belong the mushrooms and 

 puffballs. 



256. Class II. Ascomycetes. — The Ascomycetes are charac- 

 terized by the sack-like sporangium, the ascus. This is formed 

 from the terminal cell of a hypha, the two nuclei of which fuse 

 and then divide, usually three times so that eight spores are 

 formed. Not all of the protoplasm of the ascus is used in the 

 formation of the spores. The asci are usually clustered in 

 characteristic fruiting bodies. Sexual reproduction by oogonia 

 has been observed in a few cases. 



