GASTEROMYCETES 



485 



like eggs, at the base of the fructification. These have the unfortunate 

 name "peridioles." They do not open by themselves and the spores are 

 only freed by injury or by decay of the hard wall. At high temperatures 

 they germinate to strong, binucleate, clamp mycelia, which break up into 

 oidia under certain conditions of nutrition. 



In the Nidulariaceae, a part of the fructification, the peridiole assumes 

 the task of propagation instead of the basidiospores, which, on account 

 of their angiocarpous formation, are no longer shot away, and which, 

 surrounded by a gel, are set free very late. Thus the biological effect of 

 the functional degeneration of the basidia is partially compensated. 



Fig. 309. — Nidularia pisiformis. Development of basidia. (X 1,200; after R. E. Fries, 



1911.) 



Hydnangiaceae. — In this family we return to the stage of Leucogaster 

 of the Rhizopogonaceae. Here the echinulate spores are no longer 

 imbedded in a gel and the hymenium is always compact. The first 

 member of this series is Hydnangium in which we find the beginnings 

 of several divergent lines within the family. The ontogeny of this large 

 genus has been little studied. The majority of species have a simple 

 peridium, not greatly differentiated from the texture of the trama. 

 Apparently as a degeneration phenomenon, we have a series of light-spored 

 species with progressively thinner peridia, until finally the peridium is 

 absent in some Californian species, as Gymnomyces Gardneri and G. 

 Stillingeri. In the opposite direction we get a gradual thickening of 

 the peridium and darkening of the spores, reaching a climax in Hydnan- 

 gium Fitzpatrickii, with nearly black spores and a thick peridium of 

 pseudoparenchyma. 



A still higher group of species has the peridium differentiated into 

 two layers and nearly black spores, typified by H. citrinum. Such data 

 as are available, lead one to believe that the cavities form in a hemispher- 

 ical dome just under the peridium and develop basipetally until the whole 

 glebal tissue is filled with cavities. The immature condition of a number 



