68 TETRANDRIA — TETRAGYNIA. [Potamogeton. 



decked with them, that the sylvan spirits mii;:ht repair thither and remain 

 unnippcd by frost and cold winds, until u milder season had renewed the 

 foliage of their darling abodes." 



19. Potamogeton. Limi. Pond-weed. 



* Leaves all opposite; stipules none. 



1. P. densits, L. (opposite-leaved Pond-icced) ; leaves all op- 

 posite amplexicaul ovato-acuminate oi* lanceolate. E. Bot. t. 397. 



Ditches, frequent. Fl. June, July. 'if. — Peduncles short. Head of 

 flowers small, rounded. Leaves keeled below, middle nerve or rib of 

 many longitudinal cells, with 2 and sometimes 3 lateral parallel veins on 

 each side, the inner one the strongest. 



** Leaves alternate, all submersed, with adnafe stipules. 



2. P. pectindtus, L. (fennel-leaved Pond-iveed); leaves dis- 

 tichous setaceous or linear single-nerved sheathing by means of 

 tliesr adnate stipules, spike interrupted. E, Bat. t. 323. — P. ma- 

 rinus, L. 



Rivers, lakes, and salt-water ditches. Fl. July. V-. — General habit 

 not much unlike Ruppia maritima. Chamisso and Schlechtendal make 

 2 species of this ; the one having smidl fruit or nuts, not keeled at the 

 back, (their P. filifurmis): the other having large fruit, twice the size 

 of the former and keeled at the back, (their P. pectinatus). I scarcely 

 know whether these characters are sufficient to constitute species. If 

 they are, our plants, at least all that 1 have seen in fructification, and 

 tiiere is no difference in the foliage, will belong to P. filiformis. The lat- 

 ter I possess from Gouan, marked P. marinus. Probably it is the one 

 alluded to by Dillenius as having '' large heads of flowers'' when grow- 

 ing in salt-water, {see E. Fl. p. 2;37) ; and should be sought for by those 

 who live in the neighbourhood of salt-marshes. 



*** Leaves alternate, all linear, submersed; stipules free. 



3. P. pusillus, L. (small Pond-weed); leaves narrow-linear | 

 3 — 5 nerved with obscure connecting veins, peduncles elongated. 

 E.Bot.t. 215. — 13. major; stem more compressed, leaves broader, 

 spike somewhat interrupted. P. compressus, Linn. — E. Bot. t. 

 418. 



Ditches and still water?. Fl. July. If. — The stem is here, as in all of 

 this division, more or less compressed. The leaves are more or less 

 a«ute ; the spikes oblong, compact or a little interrupted. I quite agree 

 ■with Chamisso and Schlechtendal who unite the P. compressus with P. 

 pusillus. 



4. P. fframiJietfs, L. (grassy Pond-iveed); leaves broadly lin- 

 ear obtuse 3-nerved with few and obscure connecting veins, 

 peduncle scarctdy longer than the oblong-oval spike. E. Bot. t. 

 'I'lb'd — P. obtusifolius, Mert. and Koch. — Cham, et Schlecht. in 

 LiiincEa, v. ii. p. 178. t. 4. f. 8. 



Ponds and ditches; Deptford, Norwick, Yorkshire {E. FL), Lan- 

 cashire. Fl. July. If. — Nearly allied to the last, but stouter, darker- 

 Goloured and with short peduncles, scarcely longer than the stipule of 

 the leaf from the axil of which thej* spring. Tiie middle nerve or rib is 



