444 NAIADACK.K. (I'UNMWKKU lA.MILV.) 



Ordkr m.S. NAIADACEyTi:. (roNDWKEi) Family.) 



A(iuatic lit-rbs, with sU'iidcr jointed leafy immersed stems, and perfect 

 monceeious or dioEeious flowers, destitute of floral envelopes, or with 

 scale-like sepals. Stamens 1-4: anthers 1-4-celled. Ovary Ineljed, 

 forming a l-seeded aehenium in fruit. Stigmas 1-4. Seed without al- 

 bumen. Embryo straight, curved, or coiled. — Leaves sheathing, or with 

 sheathing stipules. Flowers couimonly enclosed in a spathe. 



Synopsis. 



• Flow rs monoecious or dioecious. 



1. NAIAS. Stiginas2-4. Flowers naked. Leaves opposite or whorled. 



2. ZOSTERA. Stigmas 2. Flowers enclosed in a spatbe. Leaves alternate. 



3. ZANNICUELLIA. Stigma single, peltate. Ovaries 4, from a cup-like involucre. 



* * Flowers perfect. 



4. RUPPTA. Fruit long-peduncled, umbellate. Calyx and corolla none. 



5. POTAMOGETON. Fruit sessile, f piked. Calyx 4-leaved. 



1. NAIAS, L. 



Flowers monopcions or dioecious, axillary, sessile, destitute of calyx and co- 

 rolla. Sterile Hower monuudrous, enclosed in a spathe. Anther 4-cellcd, open- 

 ing at the apex, the filament lengthening. Feriilc flower naked ; the sessile 

 ovary pointed with the slender style. Stigmas 2-4, subulate. Ovule erect. 

 Aehenium minute. Embryo straight. Radicle inferior — Stems filiform, fork- 

 ing. Leaves opposite or whorled, linear, dilated into a short sheath at the base 

 Flowers solitary, minute. 



1. N. flexilis, Tlo-stk. Stem immersed (1°- 2° long); leaves 3 in a whorl, 

 narrow-linear, membranaceous, spreading, minutely denticulate on the margins, 

 the lower ones often remote; stigmas 3-4; aehenium elliptical, acute, smooth, 

 yellowish. (Caulinia flexiHs, WiUd.) — In ponds and still water, South Caro- 

 lina, and northward. July and Aug. — Leaves about 1' long. 



Var. ■? fusiformis. Stem (6' -12' long) almost capillary, veiy leafy 

 throughout; leaves opposite, approximate, spreading or recurved (2"-4" long) ; 

 aehenium narrowly spindle-shaped, finely reticulated, brownish. — Brackish 

 water along tlic coast. West Florida. July and Aug. 



2. ZOSTERA, L. Eel-gras.s. 



Flowers monoecious, naked ; tiie sterile and fertile ones alternately arranged 

 on the anterior edge of a flattened membranaceous spadix, and enclosed in the 

 sheath-like base of tHe leaves. Anthers oblong, I-cellcd, filled with fine filaments 

 instead of pollen-grains. Ovary fixed near the apex, containing a single pen- 

 dulous orthotropous ovule, and pointed with the subulate persistent style. Stig- 

 mas 2, capillary. Utricle bursting irregularly. Seeds striate. Cotyledons in- 

 flexed-curved, received in a longitudinal cleft of the embryo — Marine herbs, 

 with creeping stems, and narrowly linear obtuse and elongated sheathing leaves. 



