224 . CLIII. NAIADACEE (BENNETT). [ Potamogeton. 
bay, Kirk ! Kambone (Livingstonia) Lagoon, Laws, 3! Lukoma (Likoma Island ?), 
Bellingham ! 
A remarkable species, combining the habit of P. Rodbinsii, Oakes and P. pecti- 
natum, Linn., but with the basal portion quite like a Cymodocea, in texture and 
rigidity. The lower stipules have membranous edges and strong fibres, which 
become frayed at the apex. 
The following species have been recorded from the African continent, but not 
within the tropics, where, however, they are likely to occur: P. americanus, 
Cham., and P. natans, Linn., occur in both North and South Africa ; P. Friesii, 
Rupr., and P. alpinum, Balb., in South Africa; P. Zizii, Roth, P. densum, Linn., 
P. trichoides, Cham., and P. perfoliatum, Linn., in North Africa. P. Zizii, Roth, 
has also been found in Madagascar. 
4, RUPPIA, Linn.; Benth. et Hook. f. Gen. Pl. iii. 1014. 
Perianth none. Stamens 2; anthers 2-celled. Carpels 4, 1-ovuled; 
stigma sessile. Fruit of 4 long-stalked, ovoid, or oblique-ovoid achenes 
on a common peduncle. Seeds uncinate; radicle large——Submerged, 
slender, brackish-water plants. Leaves elongate, filiform; sheaths 
stipule-like. Flowers small, 2-6 (usually 2) together within the leaf-. 
sheath, on a short peduncle which mostly elongates, and becomes straight 
or spirally twisted. 
Species 1 or more ? or many sub-species? In all temperate and tropical regions. 
Leaf-sheaths inflated . - : : - . 1. BR. spiralis. 
Leaf-sheaths not inflated . A : = . 2. R. rostellata. 
1. R. spiralis, Dum. Fl. Belg. Prod. 164. Leaf-sheaths inflated. 
Peduncles spirally coiled. Drupes nearly straight.—R. maritimus, var. 
spiralis, Aschers. in Aschers. & Schweinf. Ill. Fl. Egypte, 144; Durand 
& Schinz, Conspect. Fl. Afr. v. 497. 
Upper Guinea. Senegal, Leprieur ! 
Also in Egypt. 
R. acaulis, Gay MSS., may be a small form of the above rather than of RB. 708- 
tellata, judging by the fruits, &c. It was collected in Senegal by Leprieur. 
2. R. rostellata, Koch in Reichb. Pl. Crit. ii. 66, t. 174. Leaf- 
sheaths not inflated. Peduncles short at the time of flowering, not 
spirally coiled. Drupes obliquely ovoid.—R. maritima, Rendle in Cat. 
Afr, Pl. Welw. ii. 94, not of Linn. 
Upper Guinea. Lower Niger, Vogel! 
Lower Guinea. Angola: Pungo Andongo ; in a slowly flowing salt stream at 
Salinas do Dungo, Welwitsch, 245. 
5. ZANNICHELLIA, Linn.; Benth. et Hook. f. Gen. Pl. iii. 1016. 
Male flowers: Anthers 2-4-celled; filaments slender. Female 
flower with a membranous perianth. Carpels variable; style long 
