220 CLIII, NAIADACEZ (BENNETT). [ Potamogeton. 
than in P. fluitans, floating leaves ovate or oblong-lanceolate, not plicate 
at the base; stipules blunt, large. Peduncles stout, slightly swollen 
upwards; spikes dense-flowered. Fruit large, 24 lin. long; style long, 
‘at first bent back, when ripe nearly central; dorsal ridges 3, the two 
lateral with blunt wavy tooth-like margins, slightly convex on the 
ventral margin, and with indications of small bosses, but none of the 
specimens seen are quite ripe.—Durand & Schinz, Conspect. Fl. Afr. v. 
496; A. Bennett in Dyer, Fl. Cap. vii.47. P. natans, A. Rich. Tent. Fl. 
Abyss. ii. 354, not of Linn. P. americanus, var. Richardt, Solms-Laub. 
ex Schweinf. in Bull. Herb. Boiss. ii. App. ii. 8. 
Nile Land. Eritrea: Gorge of Degerra, near Saganeita, 7200 ft., Schwein- 
JSurth & Riva, 891! Abyssinia: in ponds and streams near Adowa, Schimper, 135! 
958! Amba Sea, Schimper, 571! Shireh Province, Dillon & Petit! Mai 
Gouagoua, Quartin-Dillon ! 
Also in South Africa. 
The plant mentioned as P. natans, Linn., in Schweinfurth’s Beitr. Fl, Aethiop. 
292, is probably P. Richardi, Solms-Laub, 
3. P. Schweinfurthii, Arth. Bennett. Stems about 2 ft. long, 
branched. Lower leaves crowded, linear-lanceolate, acute, 3-4 by # in. 
tapering into the petiole, 5-nerved, the central nerve broad, consisting 
of many fine veins with flexuous cross ones; middle leaves lanceolate, 
11-nerved, 24-3 by 3 in., similar in structure to the lower ones; upper 
leaves floating, coriaceous, lanceolate to lanceolate-ovate, 10-13-nerved, 
with occasionally additional interrupted nerves, 2-23 by §-} 1D; 
petioles 2-3} in. long; stipules 1-2 in. long, acute, many-nerved, not 
winged. Peduncles stout, slightly thickened in the middle, 4-6 m. 
long, springing from the axils of either submerged or floating leaves; 
spike 14-1}? in. long, dense-flowered, moderately stout. Fruit large, 
4-gx in. long, the ventral margin nearly straight, the dorsal subrotund, 
sharply 3-keeled, with undulated margins, and slightly (irregularly) 
warted, with a tooth at the base of the outer margins. 
Wile Land. Abyssinia: Begemeder ; in Lake Tana, Schimper, 1859! British 
East Africa : at the mouth of the Babr el Arab, Schweinfurth, 1223! in the Bahr 
e] Ghazal, near the Nuer Villages, Schweinfurth, 1165! 
-A most distinct species, with the. submerged leaves like those of P. lucens (but 
half the width), the floating leaves nearest to P. heterophyllus, and the fruit much as 
in P. Richardi, Solms-Laub. The lower leaves most resembling those of this species 
occur in some of Rugel’s Floridan species of P. americanus, Cham. (P. lonchites, 
. "Tuck.), but even these are not nearly as rigid as in the present plant. It differs from 
P. lucens, Linn., by producing coriaceous floating leaves, from P. heterophylius, 
Schreb. by the rigid lower leaves, and very different fruit ; and from P. americanus, 
Cham., by the floating leaves, much smaller rigid lower leaves, and fruit. 
4, P. javanicus, Hassk. in Verh. Nat. Ver. Nederl. Ind. i. 26. 
Stem branched, filiform. Submerged leaves, sessile, narrowly linear, 
acute; floating leaves lanceolate, long-petioled ; lower stipules slightly 
- connate, the upper free, acuminate. Peduncles slender ; spikes vary128 
from 3-8 lin. long. Fruit compressed, oblique-obovate ; style straight 
