848 



750. POTAMOGETON. 



20. obtusifolius {gramineiini of Smith). 

 Stem compressed : margin roimded. L. mu- 

 eronulate, 3-5 -nerved, without intermediate 

 pai-allel veins. Spilce 6-8-flowered, as long as 

 stalk, p. 7, 8. Lakes and ponds. G. occ. 

 Eng. rare. 



21. compressus {cuspidatum of Sm.). 

 L. mucronate, many-nerved, of wMch 3 or 5 

 are stronger : lateral nerves approacMng mar- 

 gin. Stem compressed, somewhat winged. 

 Spike 10-1 5 -flowered, shorter than its stalk. 

 p. 7, 8. sm. Yorksh. So. G. 



22. pusillus. Stem nearly round. L. 

 somewhat acute, mucronulate, with 3-5 equi- 

 distant nerves. Spike 4-8-flowered, inter- 

 rupted, i or i as long as stalk. Fr. obliquely 

 eUiptic. p. 7, 8. Still water. 



a. L. nearly a line broad, compressed. — Sm. 



(S. L. about 1^ line broad. 



y. tenuissimus. L. very narrow. 



23. zostersefolius. Stem flattened. L. 

 Knear, acuminate, with 3 principal nei-ves, 

 and close parallel intermediate ones. Spikes 

 cylindrical, on long stalks. Fr. obovoid, 

 keeled. Style terminal, p. 6. Rivers and 

 lakes, e. Sc. — Bab. Koch unites this zvith 

 P. compressus. 



24. trichoides. Stem nearly round. L. 

 setaceo-Knear, acuminate, 1-nerved, veinless. 

 Stalk 2 or 3 times as long as 4-8-flowered 

 spike. Fr. semiglobose. p. 7, 8. Water. 

 Sil. Berlin. Bremen. 



b. L. linear, all alternate, with sheath at 

 base, united to stipules. Stem much 

 branched. 



25. marinus. Fr., when di-y, rounded on 

 the back. L. lineari-setaceous, acute, 1-nerved, 

 with thick cross veins. Spikes on long stalks. 

 p. 7, 8. Salt marshes. G. rare. Eng. 



26. pectiuatus. Fr., when dry, obtusely 

 triangular on the back. L. lineai-i - setaceous, 

 acute, 1-nerved, with thick cross veins. Spikes 

 on long stalks, p. 7, 8. Still water. 



27. zosteraceus. Fr. lai-ge, rounded on 

 the back, but with a prominent keel when dry. 

 L. lineal-, acuminate, 3-nerved, with connect- 

 ing veins. Lateral Nerves near the margin. 

 p. 7. Still water. Serpentine in Hyde Pai"k. 

 —Bab. 



C. All L. similar, opposite. 



28. densus. L. lanceolate, amplexicanl. 



Spikes on short stalks, recurved after flow- 

 ering. Dry Fr. rostrate, compressed, with a 

 broad keel. p. 7, 8. Water. 



j3. oppositifolius, Duby ; serratum, Linn. 



L. triangulari-ovate. 

 7. lancifolius, DC. ; setaceum, Linn. L. 

 very narrow. 



751. RUPPIA. 



1. maritima. Cells of the Anthers {sac- 

 culi) oblong. Fr. ovate, erect, somewhat ob- 

 lique at base. p. 7, 8. Stagnant water in 

 salt marshes. 



2. rostellata. Cells of the Anthers nearly 

 globose. Fr. curved, ascending from an obtuse 

 base. p. 8, 9. Bitches in salt marshes. 



3. spiralis. " Differs from rostellata in 

 the very long Fl. -stalks, which afterwards be- 

 come closely spiral at the base." — Gay. 

 I have no fm'ther description. 



752. ZANNICHELLIA. 



1. polycarpa. Fr. nearly sessile, four times 

 as long as style, p. 7-9. Sea. n. G. 



2. palustris. Fr. on short stalks, twice as 

 long as style, p. 7-9. I'resh water. 



3. pedicellata. Fi*. on pretty long stalks, 

 as long as slender style, p. 7-9. Brackish 

 water, n. G. 



753. NAIAS. 



1. major. L. linear, repando-dentate. Teeth 

 mucronate. Sheaths quite entire. Cal. of 

 barren flower 2-lobed. a. 8, 9. Still water. 

 G. occ. Fr. 



2. minor. L. narrow linear, recurved, den- 

 tate. Sheaths ciliate, denticulate. Cal. 0. a. 

 8, 9. Still water. G. occ. Fr. 



3. ala^nensis. " L. in whorled bundles, 

 linear, straight, soft, mucronate, denticulate. 

 Sheath of L. with a single tooth on each side. 

 6, 7. Bitches. Alagna in Ticino." — Poll. 



4. flexilis. L. narrow linear, finely mu- 

 cromdate, denticulate. Sheaths ciliato-denti ■ 

 culate. a. 8, 9. Lakes in a sandy soil. 

 Biuowschensee near Stettin. 



754. CAULINIA. 

 1. oceanica. L. long, linear, entire, ob- 



