488 COMPARATIVE MORPHOLOGY OF FUNGI 



results in a confused mass of chambers, whose cavities were originally- 

 connected and open at the base of the pileus. At maturity, the peridium 

 cracks off, allowing the basidiospores to be disseminated. 



This line culminates in Macowanites, where some of the larger Cali- 

 fornian species, still undescribed, reach a height of 7 cm. with a flat, agari- 

 coid cap 14 cm. in diameter. These larger forms are suggestive of the 

 higher Agaricales and were it not for the large number of intermediate 

 forms in this series, would be placed in that order, as Conard (1915) and 

 Gaumann (1926) are inclined to do in the case of Endoptychum. 



Hymenogasteraceae. — This family is characterized by the colored, 

 fusiform to citriform spores, and closely parallels the Hydnangiaceae 

 in many respects. We may look for its origin in forms like Melanogaster 

 of the Rhizopogonaceae. The first stage is represented by Hysterog aster, 

 with deep yellow, smooth, fusiform spores, somewhat similar in shape 

 to those of Hysterangium. Its ontogeny is not well known, but the 

 gleba is filled with labyrinthiform cavities at maturity, as in Rhizopogon. 

 The peridium is somewhat differentiated from the trama and the septa 

 are said to be somewhat thicker in the center than next the peridium in 

 //. luteus (Hymenogaster luteus), but there is no trace of a columella (E. 

 Fischer, 1927). The details of the formation of tramal plates and cavities 

 was not studied. The peridium of H. fusisporum {Hymenogaster 

 Barnardi) is less well developed. 



The large, central genus of this family is Hymenogaster, corresponding 

 to Hydnangium of the Hydnangiaceae. Here we have an assemblage 

 of species which ontogenetic investigations will probably show to belong 

 to several series, if not to different genera. The spores are usually 

 citriform, yellow to brown, and often variously roughened. 



In an unidentified species which Fischer (1927) places in the group 

 of H. lilacinus or of H. populetorum, probably in the former if my inter- 

 pretation of his figures of immature specimens is correct, cavities form in a 

 dome-shaped area under the pseudoparenchymatous(?) peridium and 

 gradually develop basipetally. Growth is centrifugal from the central 

 ground tissue. If this method of development should be found typical, 

 it might explain a large section of the genus where the basal portion of the 

 fructification remains sterile until quite late in its development, such as 

 we find in the H. tener group (Fig. 311, A to C). In //. Behrii this 

 tissue remains as a highly differentiated hemispherical basal portion from 

 which thick septa radiate toward the peridium, as we have seen in 

 Hydnangium pusillum and Lycogalopsis and shall see again in Jaczewskia. 

 In Hymenogaster fragilis this base is prolonged into a stipe below, sug- 

 gesting Lycoperdon in appearance. 



In Dendrogaster we have a persistent columella. Perhaps the most 

 primitive species is D. candidus, where the sterile base is prominent and 

 the columella relatively small. The peridium is pseudoparenchymatous 



