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 soft, fleshy or nearly so, usually soon decaying ; dried plants do not revive well when moistened. .........................

1

Plants tough, either fleshy or gelatinous, membranaceous, corky or woody, persistent, reviving when moistened.

13

1-

Gills acute on the edge................

2

Edge of the gills obtuse, or gills fold-like, or vein-like, but prominet.....................................................................................

12

2 -

Trama of the pileus of interwoven threads, not vesiculose.

3

Trama of the pileus vesiculose, plants rigid but quite fragile .....................................................................................

11

3 -

Gills thin, not much broadened toward the pileus.....

4

Gills broadened toward the pileus, of waxy consistency.

Hygrophorus.

110

4 -

Stipe central or sub-central. (Some species of Pleurotus are sub-central, but the gills are usually not decurrent.)

5

Stipe on one side of the pileus, or none, rarely with the stipe sub-central. (Some species of Clitocybe are subcentral.) ........................................................................

Pleurotus. . .

102

5 -

Stipe fleshy, pileus easily separating from the stipe, gills usually free...................................................................

6

Stipe fleshy or fibrous and elastic, pileus confluent with the stip and of the same texture..............................

7

Stipe cartilaginous, pileus confluent with the stipe, but of a different texture......................................................

9

6 -

Vola and annulus present on the stip...........................................

Amanita. . .

52

Vola present, annulus wanting...................................................

Amanitopsis.

74

Vola wanting, annulus present...................................................

Lepiota. . .

77

7 -

Annulus and volva wanting...............

8

Annulus usually present (sometimes vague), volva wanting, gills attached to the stipe............................................

Armillaria.

83

8 -

Gills Sinuate......................................................................................

Tricholoma. .

87

Gills decurrent, not sinuate...............................................................

Clitocybe. . .

. 89

9 -

Gills not decurrent, pileus umbilicate................................................

Omphalia. . .

100

Gills not decurrent...........................................................................

10

10-

Margin of pileus at first involute, pileus flat or nearly so, somewhat fleshy (some plants rather tough and tending toward the consistency of Marasmius)........

Collybia. . .

92

Margin of the pileus at first straight, pileus slightly bellshaped, thin........................................

Mycena. . .

93

Gills usually free, pileus deeply plicate so that the gills are split where they are attached to the pileus, pileus membranaceous, very tender but not diffluent.......

Hiatula.

11 -

Plants where bruised exuding a milky or colored juice.............

Lactarius. . .

114

Plants not exuding a juice where bruised........

Russula. . .

125

12 -

Gills decurrent, dichotomous, edge blunt.........

Cantharellus.

128

Gills not decurrent, plants parastic on other mushrooms.

Nyctalis.

13 -

Edge of gills not split into two lamina?..........

14

Edge of gills split into two laminae and revolute........................

Schizophyllum.

136

14 -

Plants leathery, either fleshy, membraneous, or gelatinous...........................................................................

15

Plants corky or woody (placed by some in Polyporaceae).

Lenzites.

15 -

Stipe separate from the pileus (hymenophore), easily separating.....................

16

Stipe continuous with hymenophore...........

17

16 -

Plants tough and fleshy, membranaceous or leathery..................

Marasmius. .

130

Plants gelatinous and leathery.............

Heliomyces.

17 -

Edge of the gills acute.................

18

Edge of the gills obtuse......................................................................

19

18 -

Edge of gills usually serrate..............

Lentinus. . .

134

Edge of gills entire..................

Panus. . . .

134

19 -

Gills dichotomous...................

Xerotus.

Gills fold-like, irregular................

Trogia. . . .

137

There are only a few rare species of Hiatula, Nyctalis, Heliomyces and Xero-tus in the United States. None are here described.

The Ochre-Spored Agarics.

(The spores are yellowish brown or rusty brown.) Gills not separating readily from the pileus.......

1

Gills sometimes separating readily from the pileus, forked or anastomosing at the base, or connected with vein-

Paxillus. . .

165

1-

Universal veil not arachnoid (i. e., not cobwebby).....

2

Uuiversal veil arachnoid, distinct from the cuticle of the pileus, gills powdery from the spores.........

Cortinarius.

161

2 -

Stipe central.....................

5

Stip eccentric or none..........................................................................

Crepidotus.

159

3 -

Volva or annulus present on stipe............

4

Stip with an annulus............................................................................

5

4 -

Stip with a volva. Locellina (not reported in U. S.)...........................

Pholiota. . .

150

Stipe with a volva. Locellina (not reported in U. S.).................

5 -

Gills free from the stem.......................................................................

Pluteolus.

Gills attached.....................

6

6 -

Gills not dissolving nor becoming powdery........

7

Oills dissolving into a gelatinous or powdery condition, not diffluent as in Coprinus ................................................

Bolbitius. . .

163

7 -

Stipe fleshy......................

8

Stipe cartilaginous or sub-cartilaginous.........

10

8 -

Gills somewhat sinuate......................................................

9

Gills adnate or decurrent................

Flammula.

156

9 -

Cuticle of the pileus silky or bearing fibrils........

Inocybe. .

158

Cuticle of pileus smooth, viscid.............

Hebeloma.

157

10 -

Gills decurrent.....................

Tubaria.

159

Gills not decurrent................................................................................

11

11 -

Margin of pileus inflexed................

Naucoria. .

153

Margin of pileus straight, from the first.........

Galera. . . .

155

No species of Pluteolus are here described.

The Rosy-Spored Agarics.

(The spores are rose color, pink, flesh or salmon color.)

Stipe central.....................

1

Stipe eccentric or none and pileus lateral.........

Claudopus.

149

1-

Pileus easily separating from the stipe, gilis free.....

2

Pileus confluent with the stipe and of the same texture, gills attached, in some becoming almost free......

3

2 -

Volva present and distinct, annulus wanting.......

Volvaria. . .

140

Volva and annulus wanting...............

Pluteus. . .

138

3 -

Stipe fleshy to fibrous, margin of pileus at first incurved.

4

Stipe cartilaginous...................

5

4-

Gills sinuate.........................................................................................

Entoloma. . .

143

Gills decurrent.....................

Clitopilus. . .

142

5-

Gills not decurrent (or if so only by a minute tooth), easily separating from the stipe...............

6

Gills decurrent, pileus umbilicate.............

Eccilia. . . .

148

6-

Pileus slightly convex, margin at first incurved......

Leptonia. . .

147

Pileus bell-shaped, margin at first straight and pressed close against the stipe................................................

Nolanea.

No species of Nolanea are described here.

The Brown-Spored Agarics.

(The spores are dark brown or purplish brown.)

Pileus easily separating from the stem ; gills usually free.

1

Pileus continuous with the stem : gills attached.....

2

1-

Volva wanting, annulus present. (Psalliota) ......................

Agaricus. . ..

18

Volva present, annulus wanting............

Chitonia.

Volva and annulus wanting...............

Pilosace.

2-

Veil present......................

3

Veil wanting or obsolete................

4

3-

Annulus present, gills attached.............

Stropharia . .

31

Annulus wanting, veil remaining attached to margin of pilus.......................................................................................

Hypholoma.

26

4-

Stipe tenaceous, margin of pileus first incurved.....

5

Stipe fragile, margin of pileus at first straight......

Psathyra.

5 -

Gills sub-triangularly decurrent ....................................................

Deconica.

Gills not decurrent...................

Psilocybe.

But few species of Psathyra, Deconica, Chitonia and Pilosace are noted from the United States. None are here described.

The Black-Spored Agarics.

Pileus present to which the gills are attached......

1

Pileus wanting, gills attached to a disk at apex of stem from which they radiate...............

Montagnites.*

1-

Gills more or less deliquescing, or pileus thin, membranous and splitting between the lamina? of the gills and becoming more or less plicate................

Coprinus. . .

32

Gills not deliquescing, etc................

2

2-

Spores globose, ovoid.................

3

Spores elongate, fusiform (in some species brown), plants with a slimy envelope................

Gomphidius. .

49

3-

Pileus somewhat fleshy, not striate, projecting beyond the gills at the margin; gills variegated in colorfrom groups of dark spores on the surface ..............................................

4

Pileus somewhat fleshy, margin striate, gills not variegated.

Psathyrella. .

48

4-

Annulus wanting, but veil often present.........

Panaeolus. . .

45

Annulus wanting, veil appendiculate on margin of cap. .

Chalymotta. .

48

Annulus present..................................................................

(* One American speices in Texas)

Anellaria.