PONDWEED FAMILY 25 



long; peduncles 4-7 cm. long; spike interrupted, with 2-12 flowers in each whorl; 

 fruit ovoid, 2-3 mm. long, nearly 2 mm. thick, not keeled; stigma sessile. Ponda 

 and lakes: Que, — N.Y. — Mich. — Wyo.— Alta. Je-Au. 



18. P. interior Rydb. Stem slender, branched, 3-6 dm. long; leaves linear, 

 3-15 cm. long, about 1 mm. wide, obtuse, with a strong midrib and raised or 

 revolute margins; peduncles 3-7 cm. long; spike interrupted; fruit obhquely 

 ovoid, 2-grooved on the back; stigma subsessile; free portion of the stipules 2-4 

 mm. long. P. marinus occidentalis Robbins. Ponds and lakes, especially in 

 alkah water: Ont. — N.M. — Utah— Nev. Plain — SubmonL Jl-Au. 



19. P. pectinatus L. Stem slender, much branched, very leafy, 3-10 dm. 

 long; leaves setaceous, attenuate at the apex, 3-15 cm. long, 0.1-0.5 mm. wide, 

 sometimes nerveless; stipular sheath 1-2 cm. long; free portion 3-8 nun. long; 

 peduncles filiform, 5-20 cm. long; spike interrupted, with several whorls of flow- 

 ers; fruit obliquely ovoid, 3-4 mm. long. Fresh, salt, or alkali waters: N.B.— 

 Fla. — -L. Calif. — Alaska; Eu. Plain — Submont. Jl-S. 



20. P. Robbinsii Oakes. Stem stout, widely branching, sometimes rooting 

 at the nodes, 5-10 dm. long; leaves linear, acute, crowded in 2 ranks, 7-12 cm. 

 long, 2-6 mm. wide, auricled at the point of union with the stipules; stipular 

 sheath about 1 cm. long; free portion of the stipules 1-2 cm. long, mostly lacerate; 

 peduncles 3-10 cm. long; spike interrupted, flowering under water; fruit obovoid. 

 about 4 mm. long, 3 mm. thick, 3-keeled, the middle keel sharp. Ponds and 

 lakes: N.B.—N.J.— Mich.— Ida.— Ore.— B.C. Plain. Jl-S. 



2. RUPPIA L. 



Slender water plants, widely branched and with capill 

 alternate 1-nerved leaves, with membranous sheaths. Pe- 

 filiform, at first very short, at last generally much elongated anu spu-auv uuucu. 

 Flowers consisting of 2 sessile anthers, and 4 pistils, sessile at first, in frmt long- 

 stipitate. Fruit small, more or less obliquely ovoid drupes. 



filiform 



.mX' 



mm. long; drupe about 2 mm. long or less. 



y oblique; beak 0.5-1 nun. long. o. r» .- < 



rcely oblique, almost beakless. ?. R, pectinata.^ 



3 mm. long; drupe 3-4 mm. long. 



1. R. maritima, 



2. R, pectinata. 



3. R. occidentalis. 



1. R, maritima L. Stem slender, filiform, whitish; leaves 2-10 cm. long, 

 0.5 mm. or less wide; sheaths 6-8 mm. long, with a short free tip; peduncles m 

 fruit sometimes 3 dm. long; drupes about 2 mm. long; beak almost straight or 

 curved. R. curncarpa A. Nels. In brackish or salt water, along the coasts: 

 Newf,— Tex.— Alaska— L. Calif.; occasionally in the interior, Sask.—Mex.; bur- 

 asia and S. Am. Plain Je-Au. 



2. R. pectinata Rydb. Stem intricately branched and ver>' leafy, with 

 very short internodes; leaves filiform, 3-6 cm. long, 0.5 mm. or less wide; sheaths 

 7-10 mm. long, seldom with a small rounded tip; peduncles 3-o cm. long, m 

 fruit recurved, but apparently not in a sph-al; drupe about 1.2 ^^^-J^^^^ ^,^^^ 

 an ahnost sessile stigma. In brackish ponds: Yellowstone National 1 ark, wyo. 



•Utah— Wash.— Calif. SubmonL— Mont. 



3. R. occidentalis S. Wats. Stem comparatively stout, 3-6 dm. long, with 

 very short internodes and fan-like clustered branches; leaves 7-20 cm. long, ana 

 0.3 mm. wide or less; sheaths with distinct free tip^^ often ^overlappmg jach 

 other; peduncles sometimes 5 dm. long; stipes about 

 or Dvriform. scarcelv obliaue; beak short, straight. 



In saline ponds: Neb. 



B.C. — Alaska. Plain — SubmonL Jl-Au. 



3. ZANNICHELLIA (Mich.) L. 



Slender branching aquatics, with opposite filiform leaves and sheathing mem- 

 branous stipules. Flowers monoecious, sessile, naked, usuaUy both kmas m ine 

 same axil; the staminate ones consisting of a single 2-ceIled anther, borne on a 

 pedicel-hke filament, the pistiUate ones of 2-6 sessUe pistils in ^ cup-shaped m- 

 volucre. Fruit nut-like, obliquely oblong, flattened, with a short slender beak, 

 ribbed or toothed on the back. Seed orthotropous. 



