MONOCOTYLEDONS. — FLUvtALES. Potamogeton. 193 



2. ZOSTERA. 

 Stam. and pistils separated, inserted in two rotas upon one side 



of a spader. Spatha foliaceous. Perianth 0. Barren Fl. 



Anthers ovate, sessile, alternating with the germens and upon 



the same spodix. Fertile Fl. Ovarij 1, ovate. Style bifid. 



Drupe with I seed. 

 1. Z. marina, leaves entire somewhat S-nerved^ stem roundish. 



p. 259. — Sea-shores. 



3. ZANNICHELLIA. 



3Ionoecio7is. Barren Fl. Perianth 0. Stam. 1. Fertile Fl. 

 Perianth single, of 1 leaf. Ovaries 4 or more. Style 1. Stig- 

 ina peltate. Caps, sessile. 



1. Ts.palustris, anthers 4-celied, stigmas entire^ pericarps tooth- 

 ed on the back. p. 258. — Stagnant luaters. 



4. POTAMOGETON. 



Floivers perfect, on a spadix arising from a spatha. Perianth 

 {involucre^ Rich. ?). ylnthers 4, sessile, alternating with the 

 divisions of the peria?iih. Ovaries 4. Nuts 4, 1 -seeded, ses- 

 sile. 



* Upper leaves fioating. 



1. P. nutans, upper leaves floating coriaceous oblongo-ovate pe- 

 tiolate, lower ones membranous lanceolate gradually tapering 

 into a footstalk, p. f>l . — Lakes. 



2. P. heterophyllum, upper leaves coriaceous elliptical petiolate 

 floating, lower ones membranous linear-lanceolate sessile (pe- 

 duncle clavate, Sm.). p. 57- — Lakes. 



3. P.Jluitans, upper leaves floating subcoriaceous ovato-lanceo- 

 late tapering into a rather short footstalk, lower ones long lan- 

 ceolate sessile, p. 57. — Ditches and lakes. 



** Leaves all submersed. 



4. P. perfoliatum, leaves cordate embracing the stem. p. 58.— 

 Rivers aJid lakes. 



5. P. f/e7?5MW,, leaves (all) opposite crowded ovato-acuminate ses- 

 sile, stem forked, spike of about 4 flowers, p. 59. — Ditches. 



6. P. It/cens, leaves ovato-lanceolate petiolate. p, 58. — Rivers 

 and lakes. 



7. P. crispnm, leaves lanceolate tapering scfesile remarkably 

 waved and crisped serrate, p. 58. — Ditches. 



8. P. lanceolatnm, leaves linear-lanceolate tapering at the base 

 sessile, p. 58. — Lakes. 



9. P. gramineum, " leaves linear-lanceolate alternate sessile 

 broader than the stipules, stem rounded subdichotonious." 

 p. 58. — Ditches, 



[N] 



