558 NAIAD ACE^. (PONDWEED FAMILY.) 



* * Fruit of 6 carpels {rarely 5). 



3. T. maritima, L. Scape (1-3° high) and leaves thickish, fleshy; 

 fruit ovate or oblong, acutish ; carpels rounded at base and slightly grooved 

 on the back, the edges acute. — Salt-marshes along the coast. Lab. to X. J., 

 and in saline, boggy or wet places across the continent. (Eu., Asia, etc.) 



2. SCHEUCHZERIA, L. 



Sepals and petals oblong, spreading, nearly alike (greenish-yellow), but the 

 latter narrower, persistent. Stamens 6 ; anthers linear. Ovaries 3, globular, 

 slightly united at base, 2-3-ovuled, bearing flat sessile stigmas, in fruit form- 

 ing 3 diverging and inflated 1 - 2-seeded pods, opening along the inside. — A 

 low bog-herb, with a creeping jointed rootstock, tapering into the ascendina; 

 simple stem, which is zigzag, partly sheathed by the bases of the grass-like 

 conduplicate leaves, and terminated by a loose raceme of a few flowers, with 

 sheathing bracts ; leaves tubular at the apex. (Named for Jolin and Jolm Jacob 

 Scheiirhzpr, distinguished Swiss botanists early in the 18th century.) 



1. S. pallistris, L. — Peat-bogs, X. Brunswick to X. J., westward across 

 the continent. June. (Eu., Asia.) 



3. POTAMOGETON, Tourn. Pondweed. 



Flowers perfect. Sepals 4, rounded, valvate in the bud. Stamens 4, oppo- 

 site the sepals ; anthers nearly sessile, 2-celled. Ovaries 4 (rarely only one), 

 with an ascending campylotropous ovule ; stigma sessile or on a short style. 

 Eruit drupe-like Avheu fresh, more or less compressed ; endocarp (nutlet) crus- 

 taceous. Embryo hooked, annular, or cochleate, the radicular end pointing 

 downward. — Herbs of fresh, or one in brackish, ponds and streams, with 

 jointed mostly rooting stems, and 2-ranked leaves, which are usually alternate 

 or imperfectly opposite ; the submersed ones pellucid, the floating ones often 

 dilated and of a firmer texture. Stipules membranous, more or less united 

 and sheathing. Spikes sheathed by the stipules in the bud, mostly raised on 

 a peduncle to the surface of the water. (An ancient name, composed of 

 TTora/ioj, a river, and y^irijou, a neighbor, from the place of growth.) — By fruit, 

 the full-grown fresh or macerated fruit is intended ; by nutlet, that with the 

 fleshy outer portion or epicarp removed. All except n. 19 flower in summer; 

 the month mentioned indicates the time of ripening of the fruit. 



§ 1. Leaves of two sorts ; floating ones more or less coriaceous, ivith a dilated 

 petioled blade, different inform from the thinner submersed ones. 



* Submersed leaves reduced to narrowly grass-like or filiform sessile phyllodia. 



•t- Stems rather stout ; stipules free ; spikes all emersed, cylindrical and densely 



fruited ; fruits fleshy and turgid, obliquely obovate. 



1. P. natans, L. Stem simple or sparingly branched ; floating leaves all 

 iong-petioled, elliptical or ovate, somewhat cordate at base, obtuse but with a 

 blunt point, 21 -29-nerved; upper submersed leaves lanceolate, early perish- 

 ing, the lower (later in the season) very slender (3-7' long, barely \" wide) : 

 upper stipules very long, acute ; peduncle about the thickness of the stem ; spikes 

 1-2' long ; sides of the turgid nutlet with a small deep impression in the middle ; 



