the achene --15.

14b. Perigynium firm, closely enclosing the achene --16.

15a. Perigynium less than 1 cm. long =Sedge, Carex hystericina.=

15b. Perigynium more than 1 cm. long =Sedge, Carex lupulina.=

16a. Perigynium smooth =Sedge, Carex riparia.=

16b. Perigynium hairy =Sedge, Carex filiformis.=

17a. Beak of the perigynium bent abruptly to one side
=Sedge, Carex laxiflora.=

17b. Beak of the perigynium straight
=Sedge, Carex pennsylvanica.=

ARACEAE, the Arum Family

Individual flowers small, but crowded on a fleshy spadix to form a
conspicuous spike, usually surrounded by a green or colored spathe.

1a. Leaves compound --2.

1b. Leaves simple --3.

2a. Leaflets 3, spathe pale green or purple (3-6 dm. high; spring)
=Indian Turnip, Arisaema triphyllum.=

2b. Leaflets 7-11; spathe green; spadix long and slender (3-8 dm.
high; late spring) =Dragon Root, Arisaema dracontium.=

3a. Leaves linear, sword-shape; spathe none (5-15 dm. high; early
summer) =Sweet Flag, Acorus calamus.=

3b. Leaves broader than linear; spathe present --4.

4a. Flower clusters partly underground, appearing in earliest
spring =Skunk Cabbage, Symplocarpus foetidus.=

4b. Flower clusters peduncled, in early summer --5.

5a. Leaves broadly ovate-cordate; spathe white
=Water Arum, Calla palustris.=

5b. Leaves more or less sagittate; spathe green
=Arrow Arum, Peltandra virginica.=

LEMNACEAE, the Duckweed Family

Minute leafless plants floating on quiet water; flowers exceedingly
small and seldom seen.

1a. Plant thick, ovoid, less than 2 mm. long; roots none. Two species
are reported from Michigan =Wolffia spp.=

1b. Plant flattened, with short roots --2.

2a. Roots several from each rounded plant
=Duckweed, Spirodela polyrhiza.=

2b. Root single from each rounded plant =Duckweed, Lemna spp.=

Three species are reported from Michigan, of which the commonest is
Lemna minor.

ERIOCAULACEAE, the Pipewort Family

Bog or marsh herbs, with small