GASTEROM YCETES 



483 



central cavity which constantly enlarges. This is filled by a gel which 

 probably results from the disintegration of vegetative hyphae. The origi- 

 nally spherical chambers become lenticular, whereby the thicker wall 

 tissue is formed first on the flat side, while the curved, narrow sides remain 

 connected with the ground tissue. By secondary alterations, the wall 

 tissue attains a very complicated structure and, in N. pisiformis for 

 example, is composed of not less than five layers. Outermost there is a 

 thin, hyaline, hyphal layer with gelatinous walls, then a brown layer 



Fig. 307. — Crucibulum vulgare. A. Habit, young and mature opened fructifications. 

 B. Section of young fructification showing peridioles. (After Sachs, 1855.) 



formed of slender, compact, thin-walled hyphae, then a thin sheath of 

 dark brown, much-thickened, coarse strands, then a true, strong, lacu- 

 nose wall tissue, formed of thin-walled, brown hyphae and, finally, a 

 pseudoparenchymatous layer upon which rests the hymenium. The 

 basidia are four spored; the diploid nucleus divides twice (Fig. 309); 

 in the basidium it begins a third division which is only completed in the 

 spore, hence, as far as known, the spores are binucleate from youth. The 

 basidia degenerate, the spores absorb the gel in the glebal cavity, fall off 



