476 



COMPARATIVE MORPHOLOGY OF FUNGI 



primary basidia, which compress the ground tissues into the tramal plates. 

 The primary basidia arise directly from the tramal hyphae without the 

 subhymenium characteristic of most Basidiomycetes. Meanwhile the 

 outer portion of the ground tissue differentiates the endoperidium, which 

 is composed of slender hyphae similar to those of the fibrillose layer. 

 They are intricately interwoven and partially gelatinized. Differentia- 

 tion of the glebal tissue is rapid, the younger basidia being much 

 smaller than the primary basidia. Both types of basidia are typically 

 four spored but spore numbers from one to eight are not uncommon. 



A period of rapid spore production follows, until the trama is practi- 

 cally exhausted. Capillitium threads, hyphae similar in appearance to 

 those of the mycelial layer, grow out from the columella. 



p< 



Fig. 303. — Geaster coronatus. A. Schematic section of young fructification. Geaster 

 marchicus. B. Mature fructification. (Natural size; after Rehsteiner, 1892, and E. 

 Fischer, 1900.) 



Shortly after the endoperidium has been formed, the hyphae of the 

 apex of the endoperidium become more loosely interwoven and form a 

 thickened apical disc. The disc assumes a radial arrangement, a small 

 irregular cavity appears in the center and becomes Lined with hyphae 

 from the inner portion of the endoperidium. Then the disc collapses, 

 is depressed and gives rise to the peristome. Finally the exoperidium 

 ruptures and exposes the endoperidium. 



Differing from most other Gasteromycetes, the basidiospores, myce- 

 lium and young basidia are uninucleate. When the sterigmata develop, 

 the nucleus divides a sufficient number of times to provide a single 

 nucleus for each spore. 



Development is essentially similar in Geaster coronatus (Fig. 303) . First 

 the fundament of the exoperidium is differentiated from the ground tissue, 



