82 



NAIADACEAE. 



5. ZOSTERA L. Sp. PI. 968. 1753- 



Marine plants with slender rootstocks and branching compressed stems. Leaves 2- 

 rankcd, sheathing at the base, the sheaths with inflexed margins. Spadix linear, contained 

 in a spathe. Flowers monoecious, arranged alternately in 2 rows on the spadix. Statninate 

 flower merely an anther attached to the spadix near its apex, i-celled, opening irregularly 

 on the ventral side ; pollen thread-like. Pistillate flower fixed on its back near the middle ; 

 ovary i ; style elongated ; stigmas 2, capillary ; mature carpels flask-shaped, membra- 

 nous, rupturing irregularly, beaked by the persistent style ; seeds ribbed ; embryo ellipsoid. 

 [Greek, referring to the ribbon-like leaves.] 



About 6 species of marine distribution. Besides the following one occurs in Florida and one 

 on the Pacific Coast. 



i. Zostera marina I,. Eel-grass. Grass-wrack. (Fig. 183.) 



Zostera marina I,. Sp. PI. 968. 1753. 



Leaves ribbon-like, obtuse at the apex, i- 

 6 long, i"^" wide, with 3-7 principal 

 nerves. Spadix i / -2^ / long ; flowers about 

 3" long, crowded, usually from 10-20 of each 

 kind on the spadix ; ovary somewhat vermi- 

 form ; at anthesis the stigmas are thrust 

 through the opening of the spathe and drop 

 off before the anthers of the same spadix 

 open ; the anthers at anthesis work themselves 

 out of the spathe and discharge the glutinous 

 stringy pollen into the water; seeds cylindric, 

 strongly about 2O-ribbed, about i% /f long 

 and %" in diameter, truncate at both ends, 

 the ribs showing very clearly on the pericarp. 



In bays, streams and ditches along the At- 

 lantic Coast from Greenland to Florida and on 

 the Pacific from Alaska to California. Also on 

 the coasts of Europe and Asia. Summer. 



Family 4. SCHEUCHZERIACEAE Agardh, Theor. Syst. PI. 44. 1858.* 



ARROW-GRASS FAMILY. 



Marsh herbs with rush-like leaves and small spicate or racemose perfect 

 flowers. Perianth 4-6-parted, its segments in two series, persistent or decidu- 

 ous. Stamens 3-6. Filaments very short or elongated. Anthers mostly 

 2-celled and extrorse. Carpels 3-6, i-2-ovuled, more or less united until ma- 

 turity, dehiscent or indehiscent. Seeds anatropous. Embryo straight. 



Four genera and about 10 species of wide geographic distribution. 



leaves all basal; flowers numerous on naked scapes, spicate or racemed. i. Triglochin. 



Stem leafy; flowers few in a loose raceme. 2. Scheuchzeria. 



i. TRIGLOCHIN L. Sp. PI. 338. 1753. 



Marsh herbs with basal half-rounded ligulatc leaves with membranous sheaths. Flowers 

 in terminal spikes or racemes on long naked scapes. Perianth-segments 3-6, concave, the 3 

 inner ones inserted higher up than the outer. Stamens 3-6 ; anthers 2-celled, sessile or 

 nearly so, inserted at the base of the perianth-segments and attached by their backs. 

 Ovaries 3-6, i-celled, sometimes abortive ; ovules solitary, basal, erect, anatropous. Style 

 short or none. Stigmas as many as the ovaries, plumose. Fruit of 3-6 cylindraceous ob- 

 long or obovoid carpels, which are distinct or connate, coriaceous, costate, when ripe sepa- 

 rating from the base upward from a persistent central axis, their tips straight or recurved, 

 dehiscing by a ventral suture. Seeds erect, cylindraceous or ovoid-oblong, compressed or 

 angular. [Greek, in allusion to the three-pointed fruit of some species.] 



About 9 species, natives of the temperate and subarctic zones of both hemispheres. Only the 

 following arc known to occur in North America: 



I-'ruit linear or clavate, tapering to a subulate base. i. T. palustris. 



l ; ruit neatly globose. 2. T. striata. 



Carpels 6 ; fruit oblong or ovoid, obtuse at the base. 3. T. maritima. 



Text contributed by the late REV. THOMAS MORONG. 



