208 POTAMOGETON. [class IV. ORDER HI. 



Habitat. — Ditches and slow streams; frequent. 

 Perennial; flowering in June and July. 



** Leaves alternate, sheathing, 7vifh adnate stipules. 



2. P. pectina'tus, Linn, (Fig. 265.) Fennel-leaved Pondweed. Leaves 

 linear or bristle-shaped, single-ribbed ; nuts very large, keeled at 

 the back. 



English Botany, t. .323.— English Flora, vol, i. p. 237.— Lindley, 

 Synopsis, p, 248. — Hooker, British Flora, vol. i. p. 75. 



Hoot tuberous, with long, creeping, branched steins. Ste77i very 

 slender, numerously branched, and very leafy. Leaves narrow, linear, 

 long, slender, acute, alternate, single-ribbed, dilated at the base into 

 thin, pale, membranous sheaths, elongated, and cloven at the top 

 similar to the ligula in grasses. Spikes terminal, on a slender stalk, 

 of a few interrupted flowers, which rise above the surface. 



Habitat. — In rivers, ponds, and ditches, whether of fresh or salt 

 water. 



Perennial; flowering in July. 



This is an exceedingly variable plant, especially in the size of its 

 foliage ; in clear running streams it is mostly very large, but seldom 

 produces flowers. 



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



3. P. pusillus, Linn, (Fig. 286.) small Pondweed. Leaves linear, 

 narrow, opposite or alternate, three to five nerved, with slender 

 lateral veins ; peduncle many times longer than the spike. 



English Botany, t. 215. — English Flora, vol. i, p. 236. — Liudley, 

 Synopsis, p, 249.— Hooker, British Flora, vol, i. p, 75, 



S. ma'jor ; stem more compressed. Hooker, British Flora, vol. i. p. 

 74. — P. compress'us, Linn. English Botany, t. 418, — English Flora, 

 ToL i, p. 234. 



Root fibrous. Stem slender, slightly compressed, branched, sub- 

 mersed, except the spike. Leaves alternate below, opposiie above, 

 mostly acute, under a line in breadth, often two inches long, the mid- 

 rib slightly reticulated, lateral veins towards the margin very faint. 

 Stipules hv'rddei than the leaves, sheathing. Spikes short, lateral, from 

 the axils of the leaves, at first short and close, but in maturity looso 

 and interrupted. 



/3. P. major, although distinguished by Linnssus and later botanists 

 as a species, is considered by others a variety only, a conclusion with 

 which we fully agree. 



Habitat. — Ditches, ponds, and slow streams. 



Perennial ; flowering in July, 



