306 STUDIES OF AMERICAN FUNGI. 



plant, and which is described in connection with the genera in which 

 it occurs. 



The few typical characters described here will help the student 

 to become familiar with terms applied to them. In nature, however, 

 typical cases rarely exist, and it is often necessary to draw distinc- 

 tion between differences so slight that it is almost impossible to 

 describe them. Only by patient study and a thorough acquaintance 

 with the characters of each genus can one hope to become familiar 

 with the many mushrooms growing in our woods and fields. 



CHAPTER XXIV. 



ANALYTICAL KEYS. 



By the Author. 



CLASS FUNGI. 



SUB-CLASS BASIDIOMYCETES.* 



Plants of large or medium size ; fleshy, membranaceous, leathery, woody or 

 gelatinous ; growing on the ground, on wood or decaying organic matter ; usually 

 saprophytic, more rarely parasitic. Fruiting surface, or hymenium, formed of 

 numerous crowded perpendicular basidia, the apex of the latter bearing two to six 

 (usually four) basidiospores, or the basidiospores borne laterally ; in many cases 

 cystidia intermingled with the basidia. Hymenium either free at the beginning, 

 or enclosed either permanently or temporarily in a more or less perfect peridium 

 or veil. Basidiospores continuous or rarely septate, globose, obovoid, ellipsoidal 

 to oblong, smooth or roughened, hyaline or colored, borne singly at the apex of 

 sterigmata. 



Order Gasteromycetes. Plants membranaceous, leathery or fleshy, furnished 

 with a peridium and gleba, the latter being sometimes supported on a receptacle. 

 Hymenium on the surface of the gleba which is enclosed within the peridium up to 

 the maturity of the spores or longer; spores continuous, sphaeroid or ellipsoid, 

 hyaline or colored. Puff-balls, etc. 



Order Hymenomycetes. Hymenium, at the beginning, borne on the free outer 

 surface of the compound sporophore, or if at first enclosed by a pseudo-peridium 

 or veil it soon becomes exposed before the maturity of the spores ; mushrooms, etc. 



* The sub-class Ascomycetes includes the morels, helvellas, cup fungi, etc., and 

 many microscopic forms, in which the spores are borne inside a club-shaped body, 

 the ascus. Only a few of the genera are described in this book, and the technical 

 diagnosis will be omitted. See page 216. 



