362 



COMPARATIVE MORPHOLOGY OF FUNGI 



exterior of the hymenium. From the hymenophore, a bundle of para- 

 physes penetrates the hymenium and passes through it into the inner 

 rind Ri (Fig. 243 , 2). This is more strongly developed than in Eugenea 

 and forms a pseudoparenchymatous rind, which is elevated in spots to 

 pyramidal warts. Delastria rosea, formerly included in the Terfeziaceae, 

 seems to show the highest development in this series. 



If the cover layer Ri is further developed, so that the hymenium lies 

 farther in the interior of the fructification, we have Genabea, shown some- 

 what schematically in Fig. 244. Because of the irregular course of the 

 folds and canals, most of the hymenia are cut obliquely and hence appear 

 irregularly arranged. In cross-section, however, they are crescent 

 shaped with the concave side toward the hollow passages. 



If we review the genera of the Tuberales here discussed, their relation- 

 ships may be approximately given in the following scheme : 



Tuber 



Hydpotfya 



Pachyphloeus 



Stephensia 



Pseudobalsamia 



TUBERALES 



Choiromyees 



Piersonia 



Hydnotryopsis 



Balsamia 



Geopora 



Mycogalopsis 



t 

 Sphaerozone 



* t 

 Sphaerosoma. , - - - 



t - ' 



Hydnbcystis 



Diagram XXIV. 



Genabea 



t 



I 

 Genea 



t 

 Gyrpcratera 



Thus the Tuberales form two convergent series, the probably gymno- 

 carpous Sphaerosoma-Choiromyces series and the hemiangiocarpous 

 Genea-Genabea series. In the former, from the Sphaerosoma-like Rhizi- 

 naceae, the Hydnotrya-Balsamea group arises by a strong lateral develop- 

 ment of the hymenium which causes a deepening of the folds and by a 

 localization of the asci in the interior of the passages. The hollow pas- 

 sages are filled by a loose pseudoparenchyma arising from the paraphyseal 

 layer, so that the structure of the fructifications becomes massive (Pachy- 

 phloeus-Tuber group). Subsequently the formation of hymenia is more 

 and more limited to the last blind ends of passages (Piersonia) and finally 

 these passages coalesce completely and the hymenia lie in closed chambers 

 (Choiromyees). 



The relationships of the Genea-Genabea series are not so simple. There 

 is no doubt that in the formation of their fructifications, the same mor- 



