262 MONOCOTYLODENOUS. 



with a solitary ovule. Stigma simple. Frvit indehiscent, 1- 

 colled, 1 -seeded dry. Seed pendulous, analropous. Aquatic 

 plants, with cellular leaves. 



Genus I. ZOSTERA. 



Flowers monoecious. Perianth none. Stamens and pistils 

 separated, in two rows, upon one side of the spadix. Spathe 

 foliaceous. Anthers sessile, alternating with the ovaries. 

 Drupe 1-seeded. 



1 Z Marina. Stem flexuous, terete, somewhat jointed. Leaves long, ]i« 

 near, entire, somewhat 3-nerved. ^Jii/ier slightly curved. Stylts\iox\.. Cap- 

 sule membranaceous. Grass wrack. 



% August. Salt waters. 



Genus II. CAULINIA. 



Flowers monoecious. Perianth none. Anther 1, sessile. 

 Style filitorni. Stigma 2.cleft. Capsule 1-seeded. 



1 C Flexilis. Stetfi slender, glabrous, subniersed, branching. Leaves 

 verticillate, in a whorl, linear, denticulate at the summit. Flowers solitary, 

 axillary, sessile. 



% May — July. Stagnant waters. 2-3 ft. 



Genus III. RUPPIA. 



Flowers perfect, on a spadix, arising from the base of the 

 leaves. Stamens sessile. Stigmas 4. Ovaries 4. Verianth 

 none. Fruit pedicillate. consisting of four 1-seeded drupes. 



1 R Makitima. Stem floating, glabrous. Leaves filiform, with inflated 

 sheaths. Peduncles axillary, somewhat spiral, bearing 2 naked green flow- 

 ers. Anthers 4, sessile. 



%- July. Salt marshes. 



Genus IV. POTAMOGETON. 



Flowers perfect, on a spadix arising from the spathe. Pe- 

 rianth 4-leaved. Anthers 4, sessile, alternating with the 

 leaves of the perianth. Nuts 4, l-seeded, sessile. 



1 P Fluitans. Stem branching, glabrous. Leaves floating, on long peti- 

 oles, sub-coriaceous, oval-lanceolate, the lower ones narrow, sessile, long. 

 Flowers in axillary spikes, almost submersed. 



% May — June. Stagnant waters. 2-6 ft. 



2 P Heterophyllum. Stem branching, glabrous, upper leaves opposite, 

 lanceolate, 5-nerved ; lower ones linear, sessile. Flowers crowded on the 

 spadix. 



% July — August. Stagnant waters. 



3 P Pauciflorum. Stem branching, diffuse. Leaves linear, sessile, the 

 upper verticillate, the lower alternate. Spadix 1 from each whorl of leaves, 

 bearing 4-10 flowers. 



'Zl- Through tlie summer. Shallow water. 



