ORDER SCLERODERMATALES (PLECTOBASIDIALES) 



547 



of basidia. According to Fischer these chambers arise in the lacunar 

 manner. There is great need of developmental studies before the relation- 

 ships within this order can be determined as well as to the Hymeno- 

 gastrales, from which they undoubtedly have arisen. At maturity the 

 gleba mostly becomes a powdery mass of spores with more or less capil- 

 litium. The peridium may be thin but is often several-layered and thick 

 and firm, hence the name of the principal genus, Scleroderma. The spores 

 are from four to six or more on the basidium, sessile or nearly so. They are 

 usually dark-colored. Only one family, Sclerodermataceae, appears to the 

 author to belong in this order. It is really doubtful whether the oblitera- 

 tion of the hymenial cavities is of sufficient importance to warrant the 

 removal of this family from the Hymenogastrales, especially in view of 

 the fact that Melanogaster, Leucogaster, Alpova, and others have a tend- 

 ency toward this structure. (Fig.* 179.) 



Fischer (1933) included 10 genera in the family, of which he indicates 

 five to be in doubt. Of the typical members of the family Scleroderma and 

 Pisolithiis may be noted. The former is subterranean or growing on the 

 surface of the soil. It forms rounded spore fruits, in some species reaching 

 a diameter of 10 cm. If superficial, there is a rooting mass of mycelial 

 strands, the base being sometimes slightly stipe-like. The peridium is 

 thick and at maturity more or less leathery. The surface may be smooth 

 or roughened or in some cases forming large overlapping scales. The 

 mature gleba shows numerous dark basidium-producing areas, separated 

 by sterile veins or sheets. There is no definite hymenial layer in the 

 hymenial cavities. The pyriform basidia bear two to five nearly sessile, 

 rounded or ellipsoid, smooth or sculptured spores. The basidia disappear 



Fig. 179. Sclerodermatales, Family Sclerodermataceae. Scleroderma aurantiacum 

 Pers. (A) Vertical section through an almost mature spore fruit. (B) Basidia, with 

 sessile spores, with completely obliterated hymenial cavity. (After Tulasne, from 

 Fischer, in Engler und Prantl: Die NatiirUchen PfianzenfamiUen, Zweite Auflage, 

 vol. 7a, Leipzig, W. Engelmann.) 



