442 LEMNACEJE. (DUCKWEED FAMILY.) 
with a single amphitropous ovule. Stigma minute, sessile. Fruit green. Seed - 
without albumen. Embryo thick and fleshy. — A perennial aquatic herb, with 
oblong long-petioled leaves, and a yellow erect spadix terminating the club- 
shaped scape. pw 
1. O. aquaticum, L. Rhizoma deep, fleshy; leaves acute, nerved, on 
stout terete petioles ; scape terete, thickened upward, white beneath the spadix, 
sheathed below, commonly curved. — Ponds and slow-flowing streams, Florida, 
and northward. March and April.— Leaves about 1° long. Scape 19-2? 
long. Spadix 1/-2! long; the upper flowers mostly tetrandrous. 
7. ACORUS, L. Carawus. Sweer FLAG. 
Scape flattened, leaf-like, with the lateral sessile.spadix covered with the per- 
fect flowers. Spathe none. Sepals and stamens 6. Corolla none. Filaments 
slender: anthers kidney-shaped, 1-celled, opening transversely. Ovary 2-3 
 eelled, with several orthotropous suspended ovules in each cell. Stigma minute. 
Fruit dry, gelatinous within, 1 —few-seeded. Embryo in the axis of the albu- 
men. — Perennial herbs, from a creeping aromatic rhizoma. Leaves erect, long, 
flattened, 2-edged. Scape leaf-like, elongated above the spadix. 
1. A. Calamus, L.— Wet places, Florida, and northward, apparently in- 
troduced. April.— Rhizoma rather slender, pungent. Leaves 19-2? high, 
linear-lanceolate. Scape narrower than the leaves. Spadix cylindrical, yellow- 
ish, 2! - 3! long, spreading. š , 
OrDER 136. LEMNACEÆ, (Duckwerp FAMILY) 
Minute aquatic floating plants, with lenticular proliferous stems (fronds), 
and usually simple roots, pendent from beneath. Flowers monæcious, 
mostly from a marginal cleft of the. stem. Spathe membranaceous, — 
pitcher-shaped, bursting into two unequal lobes, soon vanishing, commonly . 
enclosing two sterile flowers, which are reduced to single slender filaments 
bearing a 2-celled anther, and a single sessile 1-celled ovary; which forms 
in fruit a 1-7-seeded utricle. Embryo straight, in the axis of fleshy 
albumen. on 
l LEMNA, L. DvckwEEp. eT M 
 Spathes marginal, 3-flowered. Anthers opening transversely. Stigma fumo - 
form. Ovules erect from the base of the cell, anatropous or halfanatropoU* 
Stems increasing by lateral buds. Roots terminating in a calyptrelike 2p" 
age. — The flowers of these plants are seldom seen. 
1. L. minor, L. Stems pale, round-obovate, 
