POND-WEED FAMILY 519 



perfect flowers without a perianth ; stamens 2 ; carpels 4, at first 

 sessile, afterwards each raised on a long stalk. (Named in honour 

 of H. B Ruppius, a botanist of the 18th century.) 



1. R. maritima (Spiral Tassel Pond-weed). — A much-branched, 

 thread-like plant, with the habit of Potamogeton pectindtus, 2 feet 

 or more long j leaves 1 — 3 in. long, with inflated sheaths ; -flower- 

 stalk becoming spirally coiled, and 5 — 6 in. long, when in fruit ; 

 ovate carpels with short beaks, on stalks, 1 — 2 in. long. — Brackish- 

 water ditches ; rare. — Fl. July — September. Perennial. 



2. R . r st ell at a 

 (Beaked Tassel Pond- 

 weed). — A more com- 

 mon form, differing in 

 the small, close sheaths 

 of its leaves, its short, 

 not spiral flower-stalk, 

 and the oblique base of 

 its carpels. — Fl. July, 

 August. Perennial. 



5. Zannichellia 

 (Horned Pondweed). — 

 Slender, submerged 

 plants, with linear leaves 

 with sheathing bases 

 and adherent stipules; 

 minute, axillary, gener- 

 ally monoecious flowers 

 without a perianth ; 

 stamen 1 ; carpels 2 — 6 ; 

 stigmas peltate. (Named 

 in honour of J. J. Zan- 

 nichelli, a Venetian 

 botanist.) 



1. Z. palustris (Common Horned Pond-weed). — A submersed 

 aquatic with the habit of the preceding genus ; stem slender, 

 3 — 6 in. long, with spreading branches ; opposite, thread-like 

 leaves 1 — 3 in. long ; flowers axillary, sessile or nearly so ; stamen 

 \ — 1 in. long, with 4-chambered anther ; carpels 2 — 4, sessile, 

 with short styles and small, crenulate stigmas. — Ditches ; common. 

 — Fl. May — August. Annual. 



2. Z. brachystemon, the commonest form, differs in having a 

 stamen only a quarter as long, with a 2-chambered anther, and a 

 larger stigma. 



r6ppia marItima {Spiral Tassel Pond-weed). 



