Potamogeton. | CLIII, NAIADACEA (BENNETT). 221 
with the ventral margin; dorsal margin 3-keeled, and strongly repand- 
denticulate, ventral nearly straight, with a projection in the centre, 
tapering to either end, variable as to the teeth-like projections on 
various parts of the fruit, which are strongest on the Australian forms. 
—P. tenuicaulis, F. Muell. Fragm. i. 90, 244. P. parvifolia, Buchen. 
in Abhandl. Naturw. Ver. Bremen, vii. 32. P. huillensis, Welw. ex 
Schinz in Ber. Schweiz. Bot. Gesell. i. (1891) 61; Durand & Schinz, 
Conspect. Fl. Afr. v. 495; Rendle in Cat. Afr. Pl. Welw. ii. 94. 
Upper Guinea. Niger Territory : Nupe; ina deep lake near Jeba, Barter, 
1069! 
Wile Land. British East Africa: at the mouth of the Bahr el Arab, Schwein- 
a 1225! Niamniam ; inthe River Rei (Rye), near Gumango Hill, Schweinfurth, 
2909 ! 
Lower Guinea. Angola: Huilla; in streams near Catumba, Welwitsch,. 
248! River Cunene, Schinz, 1001! 
Mozamb. Dist. British Central Africa: North-west Kalahari, Schinz! (in 
Herb. Buchenau). 
Also in South Africa, Madagascar, Australia, the Malay Archipelago and 
Tropical Asia. 
5. P. crispum, Linn. Sp. Pl. ed. i. 126. Stem compressed, 
slender, branched. Leaves all similar, sessile, semiamplexicaul, strap- 
shaped oblong or oblong, variously undulate, strongly serrate at the 
apex, less so on the margins; stipules small, subobtuse, lower soon 
decaying. Peduncles between the forks of the stem, rather stout, 
tapering towards the apex; spike large, lax-flowered, Fruit large, 
acuminate, compressed, obliquely-ovoid; beak very long and curved. 
—Durand & Schinz, Conspect. Fl. Afr. v. 493. 
Nile Land. Abyssinia: Nubia, Kotschy, 20! Bahr el Tussuf, Steudner, 
212! Kordofan, Kotschy, 366! Cienkowsky! Senaar, ex Durand & Schinz. 
Mozamb. Dist. British Central Africa: Nyasaland; in Roangwa (Loangwa 
River ?), Lake Nyasa, Kirk ! 
Widely distributed in all warm and temperate regions. 
6. P. lucens, Linn. Sp. Pl. ed. i. 126. Stem stout, branched. 
Leaves all submerged; lower ones lanceolate or lanceolate-linear, 
acuminate, with petioles gradually lengthening to 1-1} in., the lowest 
sessile; upper leaves lanceolate to ovate, acute, slightly firmer in texture: 
than the lower ; stipules long, beaked or winged. Peduncles 2-9 in. 
long ; stout, tapering upwards; spikes 14-2 in. long, dense-flowered. 
its large, slightly acuminate, slightly convex on the ventral margin, 
nearly semicircular on the dorsal, slightly keeled. 
Mile Land. Eritrea: Asmara, 7500 ft., Schweinfurth & Riva, 2110! 
British East Africa; in the Nile, Speke & Grant ! 
Also in Europe, Asia and America. 
Var. fluitans, Coss. et Germ. Fl. Env. Paris, ed. i. 571. Leaves much longer 
than in the normal form, up to 10 in. long, usually narrower, much darker in 
colour, drying blackish-green, with longer petioles, ascending, not semi-patent as in 
the normal form.—P. longifolium, Gay in Poir. Encycl. Suppl. iv. 535. P. macro- 
phyllus, Wolfg. in Roem. & Schultes, Mant. iii. 358. 
