220 CLiii. NAiADACEiE (bennett). [Potamogetou. 



than in P.Jiuitans, floating leaves ovate or oblong-lanceolate, not plicate 

 at the base; stipules blunt, large. Peduncles stout, slightly swollen 

 upwards ; spikes dense-flowered. Fruit large, 2J 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. oiatans, A. Rich. Tent. Fl. 

 Abyss, ii. 354, not of Linn. P. americanus^ var. Pichardi, Solms-Laub. 

 ex Schweinf . in Bull. Herb. Boiss. ii. App. ii. 8. 



irile Ziand. Eritrea : Gorge of Degerra, near Saganeita, 7200 ft., Schwein- 



J'urth Sf JRiva, '891 ! Abyssinia : in ponds and streams near Adowa, Schimper, 135 ! 

 958 ! Auiba Sea, Schimper, 571 ! Shireh Province, Dillon Sf Petit ! Mai 

 Gouagoua, Quartin-Dillon ! 

 Also in South Africa. 

 The plant mentipned as P. nutans, Linn., in Schweinfurtb's Beitr. Fl. Aethiop. 



292, is probably P. Richardi^ Solins-Laub. 



3. P. Schweinfarthii, Arth. Bennett. Stems about 2 ft. long, 

 branched. Lower leaves crowded, linear-lanceolate, acute, 8-4 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, 2J-8 by | in., similar in structure to the lower ones: upper 

 leaves floating, coriaceous, lanceolate to lanceolate-ovate, 10-13-nerved, 

 with occasionally additional interrupted nerves, 2-2 J by |-J in. ; 

 petioles 2-3J in. long ; stipules 1-2 in. long, acute, many-nerved, not 

 winged. Peduncles stout, slightly thickened in the middle, 4-6 in. 

 long, springing from the axils of either submerged or floating leaves ; 

 spike IJ-lJ in. long, dense-flowered, moderately stout. Fruit large, 

 -J-^\^ 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. 



irile land. Abyssinia : Begemeder ; in Lake Tana, Schimper, 1359 ! British 

 East Africa : at the mouth of the Bahr el Arab, Schioeinfurth, 1223 ! in the Bahr 

 el Ghazal, near the Nuer Villages, Schweinf urth, 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. heterophyllus, 

 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. 'l^. 

 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 varying 

 from 3-8 lin. long. Fruit compressed, oblique-obovate ; style straight 



