204 



J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



Stem-anatomy: The epidermis has a one-layered pseudo-hypoderma, but no 

 subepidermal strands are observed. Cortically there is only the ligular circle of 

 bundles. Endodermis of M-cells. The arrangement of the central bundles varying, 

 like that of P. lucens, from eight-bundled to oblong type. " 



Unquestionably the species very much approaches to P- 

 illinoensis. Especially the fruit-form is much the same in the two 

 species. The rostrum, however, seems to be a little longer in P. 

 capensis. The leaf-form is narrower and the submersed leaves 

 lack a lacunar system along the lateral nerves. Nor do they 

 present the recurved form and position as in P. illinoensis. 



From the hybrid P. Zizii it differs by the fruit, the narrower 

 peduncles, longer petioles, and obtuser leaf-apexes. 



It differs from all non-coriaceous-leaved species of the Lu- 



centes by its upper leaves, and from P. ziziiformis, besides, by the 



absence of subepidermal cauline strands, occurring in P. ziziiformis. 



P. lucens, dentatus, malaianus and gram.ineus and others have 



sharper-pointed submersed leaves, some of them even long-pointed. 



Distribution. Africa. Cape. Zbyher (hb. Lund.); Zwart- 



kopsrivier (Distr. Uitenhage) 1830 (hb. Stockholm.), one sheet 



signed »919!>, another 2 8799» ; Prom. BonaiSpei.DREGE (hb. Uppsal.); 



In aquosis Mathibis Kom, in prov. Delagoa, 86, Bolus (hb. Uppsal.), 



labelled: sHerb. Normals Austro-Africanum conflaverunt Macowan 



B iMinti/ et Bolus. Regio orientalis n:o 1393. Pot. lucens. L.a; Natal, 



Umschlangwe River, 93, R. Schlechter n:o 3120 (hb. Stockholm 



et Ziirich, labelled P. lucens L.). 



P. Cliamlssoi Ar. Benn. 



O B'^ 11 Notes on Potamog., in Journ. of Bot., 1904, 74 — 75. 



The leaf-margin of this species is furnished with a minute, 

 frail denticulation like that of the Lucentes. The remaining 

 properties also suggest that the species must be referred to this 

 group. The anatomical diagram of the stem does not differ very 

 much from that of the foregoing: Epidermis, one-layered pseudo- 

 hyp., a full ligular circle of bundles, faintly developed «-endoder- 

 mis (0-u-end.), and a central cylinder according to the eight- 

 bundled type. 

 The specimen examined is gathered by Johnston in » Riviere de Moha, Mauri- 

 tius, 1889 '> (hb. Haun.). 



Fig. HU. P. capensis 

 ScHEELE. A, Floating leaf 

 (Capespecimen), \. B, Sub- 

 mersed leaf ffioni Cape, j. 

 C, Pistil, rt, side-view, h, 

 fi'om behind ['the Delagoa 

 plant), Y'- ^^ Fruit side- 

 view (Delagoaplant), y. 



P. gTamineus L. Sp. pi. 1753, 127. — P. keterophyllus Schreber, Spicilegium 

 fl. lips., 1771, 21. — P. graminifolius Benko, Transs., I, 1778, 123. — P. hyhridus 



