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, sphæroid 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. HYMENOMYCETES. Analytical Key of the Families. Plants not gelatinous; basidia continuous. 1 Plants gelatinous or sub-gelatinous, basidia forked, or divided longitudinally or transversely. 4 =1=--Hymenium uneven, i. e., in the form of radiating plates, or folds; or a honey-combed surface, or reticulate, warty, spiny, etc. 2 Hymenium smooth (not as in B, though it may be convolute and irregular, or ribbed, or veined). 3 =2=--Hymenium usually on the under side, in the form of radiating plates, or strong folds. The genus Phlebia in the Hydnaceae has the hymenium on smooth, somewhat radiating veins which are interrupted and irregular. One exotic genus has the hymenium on numerous irregular obtuse lobes (Rhacophyllus). =Agaricaceæ.= 17 Hymenium usually below (or on the outer surface when the plant is spread over the substratum), honey-combed, porous, tubulose, or reticulate; in one genus with short, concentric plates. =Polyporaceæ.= 171 Hymenium usually below (or on the outer surface when the plant is spread over the substratum), warted, tuberculate, or with stout, spinous processes; or with interrupted vein-like folds in resupinate forms. =Hydnaceæ.= 195 =3=--Plants somewhat corky or membranaceous, more or less expanded; hymenium on the under surface (upper surface sterile), or on the outer or exposed surface when the plant is spread over the substratum (margin may then sometimes be free, but upper surface, i. e., that toward the substratum, sterile). (Minute slender spines are sometimes intermingled with the elements of the hymenium, and should not be mistaken for the stouter spinous processes of the Hydnaceæ). =Thelephoraceæ.= 208