CXXTX. NATADEJ5. :i87 



Fresli-water or salt-marsli plants. 



Flowers in dense, many-ilowered spikes ; perianth 



4-parted ; stamens 4 1. PotamOGEton. 



Flowers 2 or luoi-e on a slender spadix; perianth 0; 



stamens 2 2. RUPPIA. 



Flowers solitary and sessile in the axils of the leaves ; 



perianth ; stamen 1 3, Zannichellia. 



Marine, submerged in the sea. 



Spadix llat, bearing anthers and ovaries in a double 



row, on its xipper side 4. Zostera. 



1. POTAMOGETON, Linn. 



Flowers bisexual. Perianth 4-parted. Stamens 4, opposite 

 tlie parts of the perianth ; anthers subsessile, 2-celled, ex- 

 trorse. Carpels 4 ; style short or ; stigma oblique. Nuts 

 4, distinct. — Kunth, I.e. p. 127 ; Endl. Gen. n. 1664. 



Caulescent, aquatic, submerged or floating plants. Leaves alternate, 

 very rarely opposite, stipulate. Stipules connate, separate from the petiole or 

 leaf, rarely joined with the petiole ni a sheatli. Spikes spadix-hke, pedun- 

 culate, nude, terminal or axillary, — P. nutans, a nearly cosmopolitan spe- 

 cies, is found in the colony. 



2. RUPPIA, Linn. 



Plowers bisexual, 2 or more sessile on a filiform, axillary 

 spadix, at first included in the leaf-sheath, then exserted. 

 Perianth 0. Stamens 2, opposite ; filaments very short, scale- 

 like ; anthers large, extrorse, 2-celled, cells parallel, distinct, 

 easily separating. Carpels 4, free, keeled at back, gradually 

 becoming stalked. Drupes 4 or fewer, on long stalks, com- 

 pressed, gibbous, crowned with the sessile, discoid stigma. — 

 Xunth, I c. p. 122 ; Endl. Gen. n. 1661. 



R. maritima is a small submerged plant, growing in estuaries or some- 

 times in fresh or brackish water, near the sea. It has much the aspect of 

 ZannichelUa, but different floral characters. I gathered it in 1838 in a 

 " Vley," near the Lighthouse, Greenpoint ; fruiting in December. 



3. ZANNICHELLIA, Mich. 



Plowers monoecious or polygamous (male and bisexual), 

 solitary in the axils of the leaves, sessile. Perianth 0. IStale : 

 Stamen 1 ; filaments filiform ; anthers 2-celled, cells divergent 

 at base. Hermaphrodite: Stamen 1, lateral. Carpels 4, 

 free, convex-backed, sessile, with a short cup-like sheath at 

 base ; ovule solitary, pendulous ; style short ; stigma peltate, 

 disk-like. Nuts 4, subsessile or stipitate, oblicpiely oblong, 

 compressed, beaked with the persistent style, more or less 

 toothed or crested at hAC^.—Kunth, I. c. p. 123 ; Endl. Gen. n. 



1662. 



2 c 2 



