324 BOTANY. 



cetes must be considered as involved in much doubt. Two 

 orders may be readily separated in this class, the Gasteromy- 

 cetes and the Hymenomycetes. 



418. Order Gasteromy cetes. The plants of this order 

 are saprophytes, producing sporocarps which are often of 

 large size, and usually of a more or less globular outline, 

 sometimes long-stalked. The spores are always borne in the 

 interior of more or less regular cavities, and from these they 

 escape by the drying and rupture of the surrounding tissues. 

 419. The mycelium of the Gasteromycetes penetrates the 

 substance of decaying wood, and the soil filled with decaying 

 organic matter. It is composed of colorless jointed hypha?, 

 which usually aggregate themselves into cylindrical root- 

 like masses. After an extended vegetative period, the my- 

 celium forma upon its root-like portions small rounded 

 bodies, the young sporocarps, which increase rapidly in size, 

 and assume the form characteristic of the different genera. 



420. The sporocarps are composed of hyphae which are 

 much interlaced ; in the interior they are more loosely ar- 

 ranged, while externally they form a more or less well-defined 

 limitary tissue, the peridium. In some genera the peridium 

 is composed of two or more layers, as in the Earth-star ( U wit- 

 ter). The spores are borne upon hymenial layers which line 

 cavities in the interior of the sporocarp. The basidia upon 

 which the spores are borne are the rounded or elongated ter- 

 minal cells of hypha-branches ; each basidium bears four or 

 more (frequently eight) spores upon the ends of as man} 

 small projections (spicules). In Phallus and its allies the 

 hymenial cavity lies beneath the double peridium and paral- 

 lel to its surface ; when the spores are formed, by the rapid 

 growth of the axial portion of the sporocarp, the hymen him 

 is carried up through a rent in the apex of the peridium and 

 the spores thus set free. In the Earth-star (Geaster), Puff- 

 ball (Ly coper don), and their allies, the hymenial cavities are 

 numerous, of irregular shape, and scattered through the tis- 

 sue of the sporocarp. The spores are set free by the rupture 

 of the peridium, and the drying of the whole sporocarp, 

 thus reducing its interior hyphae to a fine powder. In the 

 Puff-ball the single peridium ruptures irregularly, but in the 



