26 ZANNICHELLIACEAE 



1. Z. palustris L. "Stem cai)illary from a creeping rhizome; leaves 3-7 cm. 

 long, 0.5 mm. or less wirle, acute, thin, l-ncrved; fruit 2-6 together, 2-4 mm. 

 long, sessile or short-]ieilicelleci; style persistent, 1-2 mm. long. In fresh and 

 brackish ponds and ditches: Ont. — Fla. — Tex. — Calif. — -B.C.; also in the Old 

 World. Plain — Siibmont. Jl-0. 



Family S. NAJADACEAE. Naj.\s Family. 



Slender submerged aquatic plants, with linear spinulose-toothed whorled 

 or opposite leaves, sheathing at the base. Flowers monoecious or dioecious, 

 solitary and axillary. Staminate flowers with a double perianth, the inner 

 hyaline; stamen 1. Pistillate flowers of a single pistil, with 2-4 subulate 

 stigmas. Fruit a small drupe. 



1. NAJAS L. 

 Characters of the family. 



Leaves 1-3 mm. wide, coarsely toothed; back of the leaves and internodes spiny; plant 

 dioecious. 1. jV. marina. 



Leaves 0.5—1 mm. wide, finely, almost microscopically serrulate; back of the leaves and 

 internodes imarmed; plant monoecious. 

 Drupe sliining, with 30-.50 rows of indistinct reticulations. 2. iV. fleiiUs. 



Drupe dull, with 16-20 rows of strongly marked reticulations. 3. N. guadalupensis. 



1. N. marina L. Stem stout, compressed, generally armed with teeth 

 twice as long as broad; leaves broadly linear, 12-45 mm. long, with 6-10 spine- 

 pointed teeth on each margin; sheaths broadly rounded; their margins entire or 

 with a few teeth; fruit 4—5 mm. long; epicarp as well as the dull mitlet rugose- 

 reticulate. In lakes and ponds with fresh or brackish water: N.Y. — Fla. — L. 

 Calif. — Calif, (in the range reported only from Utah); Eurasia and Austr. 

 Plain. Jl — -Au. 



2. N. flexilis (Willd.) Rost. & Schmidt. Stem slender, forking, unarmed; 

 leaves narrowly linear, 1-2 cm. long, munerous and crowded, pellucid, with 20- 

 30 minute teeth on each margin; sheaths rounded, with 5-10 teeth on each side; 

 fruit ellipsoid, 2-3 mm. long. In ponds and slow streams: Que. — Fla. — La.— 

 CaUf.— Ore.; Eu. Plain. My— Au. 



3. N. guadalupensis (Spreng.) Morong. Stem very slender, filiform, 3-6 

 dm. long, branched and leafy; leaves numerous, crowded, 12-25 mm. long, 0.5-1.5 

 mm. wide, with 40-50 teeth on the margins; sheaths as in A'^. flexilis; fruit about 

 2 mm. long. N. microdon R. Br. In ponds and lakes: Neb. — ^Fla. — La. — Tex. 

 — Ore.; Mex. and Trop. Am. Plain. Jl-S. 



Family 9. SCHEUCHZERIACEAE. Arrow-grass Family. 



Marsh plants, with terete rush-like leaves and small perfect, spicate or 



racemose flowers. Perianth-segments 4 or 6, in two series. Stamens 3-6; 



anthers 2-celled. Carpels 3-6, 1-2-ovuled, more or less united, separating 



at maturity, either dehiscent or indehiscent. Seeds anatropous. Embryo 



straight; endosperm none. 



stem scapose; leaves all basal; flowers spicate or racemose. 1. Triglochin. 



Stem leafy; flowers few, in loose racemes. 2. Scheuchzeria. 



1. TRIGLOCHIN L. Arrow-grass. 



Marsh herbs, with half-round elongated linear leaves, sheathing at the base, 

 and terminal racemes or spikes on long naked scapes. Perianth-segments in 

 ours 6, the inner 3 inserted higher up. Stamens 6; anthers 2-celled, sessile or 

 nearly so. Ovaries 3-6, 1-celled and 1-ovuled; style short or none; stigmas 3-6, 

 plumose. Fruit of 3-6, cylindraceous, oblong, obovoid, or clavate carpels, 

 united at first, at maturity separating from the base upwards. Seeds cylindra- 

 ceous or ovoid-oblong, compressed or angular. 



Carpels 3; fruit linear-clavate, tapering at the base. 1. T. palustris. 



Carpels 6; fruit oblong or ovoid, obtuse at the base. 2. 7 . maritima. 



