8b. Spikes not in dense heads, nor white-woolly at maturity --9.

9a. Perennial by a creeping rootstock =Nut Gra.s.s, Cyperus esculentus.=

9b. Perennial by hard basal corms =Cyperus, Cyperus strigosus.=

10a. Bracts of the spike chestnut-brown =Twig Rush, Cladium mariscoides.=

10b. Bracts of the spike green or straw-color (Sedge) --11.

11a. Spikes 3-8, separate =Sedge, Carex straminea.=

11b. Spikes very numerous and densely crowded =Sedge, Carex vulpinoidea.=

12a. Achenes flattened =Sedge, Carex crinita.=

12b. Achenes 3-angled --13.

13a. Perigynium tipped with a sharp straight 2-toothed beak --14.

13b. Perigynium with a short soft beak --17.

14a. Perigynium thin and papery, loosely enclosing 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 cl.u.s.ters partly underground, appearing in earliest spring =Skunk Cabbage, Symplocarpus foetidus.=

4b. Flower cl.u.s.ters peduncled, in early summer --5.

5a. Leaves broadly ovate-cordate; spathe white =Water Arum, Calla pal.u.s.tris.=

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 flowers in heads terminating long slender scapes.

One species in Michigan; leaves linear and basal; flower-stalk 5-15 cm.

high; flower-heads whitish or lead-color =Pipewort, Eriocaulon articulatum.=

XYRIDACEAE, the Yellow-eyed Gra.s.s Family