tum), warted, tuberculate, or with
stout, spinous processes; or with
interrupted vein-like folds in resupinate
forms. =Hydnaceae.= 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 Hydnaceae). =Thelephoraceae.= 208

Plants more or less fleshy, upright
(never spread over the surface of the
substratum), simple or branched. Hymenium
covering both sides and the upper
surface. =Clavariaceae.= 200

=4=--Basidia forked or longitudinally
divided; or if continuous then globose,
or bearing numerous spores; or if the
plant is leathery, membranous, or
floccose, then basidia as described.
Hymenium covering the entire free
surface or confined to one portion;
smooth, gyrose, folded or lobed; or
hymenium lamellate, porous, reticulate
or toothed forms which are gelatinous
and provided with continuous basidia may
be sought here. =Tremellineae.= 204

FAMILY AGARICACEAE.

Pileus more or less expanded, convex, bell-shaped; stipe central or
nearly so; or the point of attachment lateral, when the stipe may be
short or the pileus sessile and shelving. Fruiting surface usually on
the under side and exposed toward the earth, lamellate, or prominently
folded or veined. Lamellae or gills radiating from the point of
attachment of the pileus with the stipe or with the substratum in the
sessile forms; lamellae simple or branched, rarely anastomosing behind,
clothed externally on both surfaces with the basidia, each of which
bears four spores (rarely two), cystidia often present.

Key to the North American genera.

THE WHITE-SPORED AGARICS.

(Sometimes there is a faint tinge of pink or lilac when the spores are
in bulk, but the color is not seen under the microscope.)

=Plants