510 CLASS BASIDIOMYCETEAE 



more fleshy Coprini the broad gills are close together but not in contact 

 and the original downward curve of the pileus keeps them in contact with 

 the stipe. Thus the outer portion of the gills furthest from the center of 

 the pileus is situated at the bottom of the gill mass. The maturing of the 

 basidia and discharge of the basidiospores occur first in a narrow band at 

 this outer edge of the gill. The spores have only a short distance to fall to 

 escape into the air. Then this band from which the spores have been dis- 

 lodged undergoes autodigestion into a dark-colored fluid which either 

 dries up or drops off and the next strip of the hymenium produces its 

 spores. Thus the spores never have to fall far between the crowded gills. 

 The black inky drops are not colored by the spores and are not the means 

 by which the latter are distributed. In the Coprini with narrow gills, quite 

 widely spaced, also in Pseudocoprinus, the tissue of the pileus is very thin. 

 It spHts radially over the median plane of each gill which spreads out in a 

 V-shaped cross section, thus making the fall of the spores more efficient. 

 Buller (1909) gave a thorough discussion of these different types of pilei. 

 In most of the remainder of the Agaricaceae the basidia reach maturity 

 not in a band but here and there all over the surface of the gills. In Pan- 

 aeolus, another dark spored genus, the spores mature in patches on the 

 gifls, giving them a more or less variegated appearance. Possibly this in- 

 dicates a tendency toward the habit in the fleshy Coprini. 



It is worthy of note that Pietro Antonio Micheli published in 1729 

 what is probably the first key to the species of this family, which he 

 recognized merely as a single genus Fungus. Among the characters used 

 by him in his key were the clustered or separate growth of the spore 

 fruits, their branching or nonbranching, presence or absence of volva, 

 presence or absence of annulus, nature of annulus, i.e., whether free or 

 attached to the stipe, presence or absence of striations on the pileus, loca- 

 tions of striations if present, whether pileus and gills were of the same or 

 different colors, presence or absence of latex, etc. Although his system, 

 too, was largely artificial it served to distinguish the species known to 

 Micheli and in some particulars was no more artificial than the one more 

 recently employed. 



In spite of the various systems of classification proposed in the last few 

 decades the relationships within the Hymenomycetes are still very un- 

 certain. The simplest forms appear to be those related to Corticium in the 

 Thelephoraceae. In many respects this genus is morphologically very 

 much like Ascocorticium of the Taphrinales. It may be that by the extru- 

 sion of the spores into external pockets the basidium has arisen from the 

 ascus and thus the gap between the Ascomyceteae and Basidiomyceteae 

 was bridged. On the other hand the basidium of a form like Auricularia 

 may represent a four-spored ascus in which the ascospores instead of 

 escaping germinate in situ and produce secondary spores. From this struc- 



