26 THE GASTEROMYCETES OF THE UNITED STATES AND CANADA 



The present plant presents some points in structure which show the difficulty in 

 separating the families Hysterangiaceae and Hymenogastraceae. In the former the 

 tramal plates arise from a sterile, more or less conspicuous base and hence the peridium 

 is readily separable from the gleba, an excellent type of this order being Hysterangium 

 clathroides. In the latter family the tramal plates arise from the peridium, and 

 hence the latter is more or less inseparable from the gleba. In the present plant 

 tramal plates usually arise entirely from the peridium but there is quite often a 

 fairly distinct sterile base or central columella from which the tramal plates also origi- 

 nate and in sections, of a few young specimens, small spaces have been observed where 

 the gleba was not even in contact with the peridium. But since the sterile base and 

 columella, when present, are almost always continuous in all directions with the perid- 

 ium, and since it is separable only with difficulty from the gleba, we are considering 

 our plant as belonging in the Hymenogastraceae. It seems clearly a Sclerogaster , as 

 shown by the presence of numerous mycelial strands which often extend out into byssoid 

 mycelial plates, the minute glebal chambers, the hymenium with long, irregularly 

 cylindrical basidia and the accompanying slightly acuminate, sterile cells (which may 

 be young basidia), and the spherical, warted spores with short stalks. Our plant 

 differs from S. compactus (Tul.) Sacc. ( = Octaviania compacta Tul. and S. lanatus 

 Hesse) in smaller size, larger spores, and fewer spores to the basidium. We have 

 examined the spores of an authentic specimen of Oclaviania compacta, through the kind- 

 ness of the Director of Kew Gardens, and find them to be subspherical, warted but not 

 strongly so, pale olivaceous under the microscope, 4.5-6/* thick. They are much less 

 rough than is shown in Tulasne's drawings, but possibly immature. Aside from micro- 

 scopic characters the present plant can readily be distinguished from other hypogenous 

 fungi, which we have observed, by its very small size, white color, minute chambers, 

 and by the very obvious byssoid mycelium. 



7474. Buried in humus mixed with cedar leaves and twigs, August 5, 1924. An ample collection of 

 about 100 plants. 



RHIZOPOGON Fr. 



Fruit body subglobose, growing on the surface of the ground or buried up to several 

 inches in humus or soil. Peridium tough, its surface more or less netted or lined with 

 adherent vein-like fibrils which fuse below into one or several threadlike rhizomorphs; 

 gleba attached to peridium, composed of small crumpled or box-like chambers which 

 are lined by a distinct hymenium and contain an empty cavity in youth, but which at 

 maturity may or may not be stuffed with spores. After maturity the gleba deliquesces 

 slowly into a deep brown slime which escapes by the decay of the peridium or its rupture 

 by insects. Basidia subclavate to nearly cylindrical, thin-walled, collapsing after the 

 spores are formed; spores smooth, elliptic, 2-8 on a basidium, the sterigmata short or 

 none, sometimes represented by a little cup which remains attached to the spore. 



Tulasne says that the spores are sessile in Rhizopogon, and in all species we have 

 studied except R. parasiticus the sterigmata are very short or absent. Zeller and Dodge 

 speak of and illustrate long sterigmata in several cases, but where we have been able to 

 check these we find the usual short sterigmata. Their fig. 2 on pi. 3, of R. roseolus, 

 we are confident is an erroneous interpretation of their material, both in the length 

 of the sterigmata and the gelatinized basidial walls. The gelatinized cells there shown 



