222 CLIII, NAIADACEZ (BENNETT). [ Potamogeton. 
Upper Guinea. Senegal: in Lake Guier, Rogers! Lepieur ! 
Mozamb. Dist. British Central Africa: Lukoma (Likoma Island?) in Lake 
Nyasa, Bellingham ! in the south-western bay of Lake Nyasa, Kirk ! 
Also in South Africa, Europe, North America and Australia. 
7. P. coloratum, Hornem. Fl. Dan. t. 1449. Stem slender, branched. 
Leaves all transparent and net-veined; the upper sometimes nearly 
sessile, very variable, elliptic to almost orbicular, never plicate at the 
base, and never (?) floating; lower lanceolate; stipules stout and 
obtuse. Peduncles slender, nearly equal in diameter throughout; 
spikes long, cylindrical. Fruit small, greenish, rounded and keeled on 
the dorsal margin when dry, but not when fresh, with no apparent 
beak.—P. plantagineus, Du Croz in Roem. & Schultes, Syst. Veg. iii. 
504; Engl: Pfl. Ost-Afr. A. 80. P. helodes, Dum. Fl. Belg. Prod. 163. 
Mozamb. Dist. German East Africa: Usambara, ex Engler. 
Also in Europe, Australia and the West Indies. 
8. P. pusillum, Linn. Sp. Pl. ed. i. 127. Stem slender, subterete, 
branched. Leaves all similar, sessile, semiamplexicaul, narrowly linear, 
acuminate, acute or subacute, 1-3-nerved, mostly without fascicles of 
leaves in the axils; stipules small, acute, or subacute. Peduncles 
slender, variable in length; spike few-flowered, 4-1 in. long, not (or 
very nearly) interrupted. Fruit small, semioval or obovoid, very 
slightly compressed, bluntly 3-keeled on the dorsal face, slightly convex 
on the ventral, generally without teeth.— Hook. Niger Fl. 181, 528; 
Durand & Schinz, Conspect. Fl. Afr. v. 496. 
Upper Guinea. Cape Verd Islands ; St. Jacob’s Island, Darwin ! Guinea, ex 
Durand & Schinz. 
Nile Land. Abyssinia: Shireh; near Arbatienseca, Quartin-Dillon ; and near 
Adowa, Schimper (ex Richard). 
Lower Guinea. Angola, ex Hooker. 
Mozamb. Dist. British Central Africa: Nyasaland ; in a pond in the 
Residency gardens at Zomba, Whyte ! 
Widely distributed in all warm and temperate. regions. 
9. P. Preussii, Arth. Bennett. Stems branched, semiterete, striate. 
Leaves all similar, linear for 2 of their length, then tapering, acute and 
acuminate, 1}—2} in, long, 1,—.3, in. broad, generally curved from the 
base to the apex towards the stem, stiffer in texture than most of the 
gramineum series, 3-nerved; central nerve of 5—9 closely packed veins 
with anastomosing cross veins ; stipules persistent, 4 the length of the 
internodes, acute, with many fine veins. Peduncles 1-2 in. long, 
slender, slightly tapering upwards; spike 4-2 in. long, dense-flowered. 
Perianth-segments rhombic-orbicular. Fruit small, slightly compressed, 
with a central beak, keels almost obsolete. 
Upper Guinea. Cameroons, Preuss, 451! Staudt, 462! 
Mile Land. Eritrea: in the Gorge of Degerra, near Saganeita, 7200 ft., 
Schweinfurth & Riva, 896! Abyssinia: near Adowa, Schimper, 179! Amba Sea, 
Schimper, 570! Shireh Province, Quartin-Dillon & Petit, 571! 
