240 MYCOLOGY 



each other by curved plates of tissue which anastomose in every direc- 

 tion. The walls of the chambers consist of layers of branched hyphse 

 bearing the basidia which line the interior walls of the cavities and con- 

 stitute the hymenium. Each basidium usually bears four spores. 

 The way the spores are borne on the basidia is characteristic. They are 

 almost sessile in Geaster, in Bovista they are found on long sterigmata. 

 Mitremyces may have as many as a dozen basidiospores, which are 

 sessile and lateral. 



When the puff-ball reaches full size and ripens, the tissues become 

 moist, deliquesce and change in color. The tissues are absorbed and 

 disappear and the whole mass dries up, leaving the interior sur- 

 rounded by the peridium filled with a dry dusty mass usually con- 

 sisting of slender threads (the capillitium) and countless multi- 

 tudes of ripe spores. The threads of the capillitium are absent in many 

 genera, but when present they are characteristic and used as important 

 points in the classification. There are two distinct kinds of capillitial 

 threads. In one kind, the threads are long hair-like strands, simple, 

 more or less branched and interwoven, proceeding from the inner walls 

 of the peridium, or from the centrally placed columella. The second 

 type, characteristic of Bovista, Bovlstella and Mycenastrum, has rela- 

 tively short and branched threads entirely separate and distinct from 

 each other and are not connected with the peridium nor the columella. 

 The bird-nest fungi are characterized by the thickening of the walls of 

 the glebal chambers to form separate little seed-hke bodies enclosing the 

 spores. These are known as peridioles. The ripe spores in some are 

 smooth, some are spinulose, while in shape they are globose, oblong or 

 oval. 



The most primitive forms of these fungi are probably the subter- 

 ranean forms included in the family Hymenogastrace^. In one 

 classification of the Gasteromycetes, the division of the famihes is 

 based on whether the sporophore is borne above or below the ground. 

 The family Hymenogastrace^ with subterranean fruit bodies belongs 

 to one division, all of the other families to the other division. 



Family i. Hymenogastrace^. — The subterranean fruit bodies of 

 these fungi suggest those of the families Terfeziace^ and Tuberace^ 

 among the ASCOMYCETALES, but the spores of the two latter 

 families are borne in asci, and are known as ascospores, while those of 

 the former family are borne on basidia and are known as basidiospores. 



