ORDER HYMENOGASTRALES 537 



Family Hymenogastraceae. The type of this family is the genus 

 Hymenogaster. This is subterranean or with the upper surface projecting 

 above the ground at maturity. In very young specimens Rehsteiner 

 (1892) showed that a pahsade layer of cells develops as a boundary setting 

 off the thick sterile base from the upper peridium. This layer arches up- 

 ward with the growth in size of the spore fruit forming a single central 

 cavity into which grow downward from the roof various branches and 

 plates which extend to and apparently in places grow fast to the base. 

 These plates anastomose with one another so that labyrinthiform hy- 

 menial cavities are formed. With the increase in size of the spore fruits the 

 relative size of the sterile base becomes much smaller. Eventually the 

 spore fruit shows very numerous irregular cavities, sometimes radiating a 

 little from the sterile base. The peridium is rather firmly attached to the 

 outer side of the gleba. The hymenial cavities are lined with clavate 

 basidia which bear two, rarely four, spores. These vary with the species 

 but are mostly ellipsoidal, ovoid or limoniform, mostly yellow to brown in 

 color, smooth or more often verrucose or wrinkled. No cystidia are de- 

 scribed for this genus. Apparently closely related to the foregoing is the 

 unilocular genus Gasterella, described by Zeller and Walker (1935) and 

 Miss Walker (1940). It grows on the surface of the soil and reaches the 

 diameter of 300 to 700 ju and even up to over 1200 m- According to Routien 

 (1939) rhizomorphs are attached to the spore fruits and their hyphae show 

 clamp connections although these are not visible in the basidiocarp. In 

 the specimens that reach maturity in the smaller dimensions the cavity 

 may have smooth walls but in the larger spore fruits the hymenium sends 

 folds and projections into the cavity from above and from the sides. These 

 greatly increase the hymenial surface but do not reach the bottom, so that 

 the spore fruit remains unilocular. The basidiospores arise in twos or more 

 often fours and are dark-colored, verrucose and somewhat apiculate. 

 When detached a piece of the sterigma often remains attached to the 

 spore. Cystidia with black verrucose heads are sometimes found, espe- 

 cially in the smaller specimens that have developed under less favorable 

 conditions. They appear to be, perhaps, aborted basidia. In the very 

 young spore fruits an arching palisade layer of densely staining cells ap- 

 pears in the midst of the loose tuft of hyaline hyphae. As it broadens and 

 arches up further a cavity is formed into which eventually push the plates 

 or folds which partially divide up the single cavity. Miss Walker (1940) 

 suggested that Gasterella should be placed in Order Protogastrales but in 

 a separate family Gasterellaceae. In the author's opinion the similarity 

 of Gasterella to the young stages of Hymenogaster rehsteineri Bucholtz is 

 too great to allow their separation into different families and orders. 

 (Fig. 173 A-E.) 



Gasterellopsis (Routien, 1940) begins its development much as in 

 Gasterella except that there is a central percurrent columella so that when 



