Zostera. NAIADACE^. jgj 



» Immersed aquatics, with flat linear leaves : ovaries solitary or distinct, 1-ovuled. — Naiade^e. 



+- Perianth none, or membranous and cup-shaped. 



++ Flowers monoecious or dioecious : ovary 1, sessile : stamen 1 (where known). 



1. Naias. Flowers dioecious, solitary or clustered, axillary. Perianth none in fertile flowers, 



cup-shaped and membranous in the staminate. Style with 2 to 4 awl-shaped stigmas. 

 Stems floating, with opposite or ternate leaves. 



2. Zostera. Naked ovaries and stamens alternate in 2 vertical rows on the inner side of a mar- 



gined leaf-like enclosed spadix ; ovaries i)eudulous. Stigmas 2, linear. Stem creei)ing. 



3. Phyllospadix. Ovaries naked, alternate in 2 rows on the inner side of a margined iblia- 



ceously appendaged enclosed spadix, ascending. Stigmas 2, linear, sessile. 



4. Lilaea. Fertile flowers in an exserted slender spike. Stigma capitate. 



++ ++ Ovaries about 4, nearly sessile, becoming more or less stipitate. 



5. Zaniiichellia. Flowers monoecious, axillary, sessile or nearly so. Stamen 1, naked ; fila- 



ment slender. Fertile flowers solitary, with a cup-shaped membranous spathe or peri- 

 anth. Stigmas peltate. Leaves opposite. 



6. Ruppia. Flowers perfect, 2 or more on an enclosed spadix, at length long-exserted, without 



perianth. Anthers 2, sessile, the cells distinct. Stigma depressed. Leaves alternate, 

 -f- +- Flowers perfect, with herbaceous 4-sepaled perianth, in a peduncled spike. 



7. Potamogeton. Ovaries and anthers 4, .sessile. Stigma sessile, unilateral. 



* * ^Marsh plants with terete bladeless leaves : flowers perfect, spicate or racemose, with her- 

 baceous 6-lobed perianth : carpels 3 or 6, more or less united, separating at maturity : seed 

 erect or ascending, anatropous, with straight embryo. — Juncagine^. 



8. Triglochin. Ovaries 3 to 6, united until maturity. Leaves radical. Flowers bractless, in 



a spike-like raceme terminating a jointless scape. 



9. Scheuchzeria. Ovaries 3, nearly distinct, at length divergent. Flowers bracteate in a 



loose raceme upon a leafy stem. 



1. NAIAS, Linn. Naiad. 

 Flowers mostly dioecious, axillary, solitary or clustered, sessile. Male flower of 

 a single stamen and a membranous tubular 4-lobed perianth within a small cup-shaped 

 membranous spathe ; anther 4-celled, nearly sessile : pollen granular. Fertile 

 flowers without perianth or spathe, the oblong ovary terminated by a short style and 

 2 to 4 narrowly subulate stigmas. Fruit a very thin membranous utricle, filled by 

 the single erect anatropous seed. Outer testa subcrustaceous. Embryo straight, 

 entire, with the minute plumule near the upper end. — Slender immersed aquatics, 

 with jointed branching floating stems, and opposite or verticillate (often crowded) 

 linear toothed leaves, sessile and somewhat dilated at base. 



Ten or twelve species are known, four of which are found in the Atlantic States. 



1. N. major, Allione. Stem rather stout and often armed with broad prickles : 

 leaves broadly linear, 3 to 18 lines long, coarsely and sharply toothed, the dilated 

 base entire : fruit 2 to 2^ lines long : seed very finely lineate, oblong, slightly com- 

 pressed. — Nees, Gen. t. 44. 



In Clear Lake (Bolander) ; Huntington Valley, Nevada ( Wheeler) ; Santa Cruz River, Arizona 

 {Dr. Smart) ; Utah, Parry. It is also found in the salt springs of New York, in Europe, the 

 West Indies, and the Sandwich Islands. 



2. N. flexilis, Rostk. & Schmidt. Stems very slender : leaves very narrowly 

 linear, a half to an inch long, very minutely serrulate : fruit 11 lines long, narrowly 

 oblong. — JV. Canadoisis, Michx. ; Hook. Fl. Bor.-Am. ii. 170", t. 184. 



Near San Francisco (Chamisso) ; Clear Lake (Bolander) ; Washington Territory {Lyall) ; com- 

 mon in the Atlantic States, and found in Mexico, the West Indies, and Europe. 



2. ZOSTERA, Linn. Eel-grass. Grass-whack. 



Flowers monoecious and without perianth, the single stamens and ovaries arranged 

 alternately in 2 rows upon the face of a linear-oblong leaf-like sessile spadix en- 



