46 P. Graebner. — Potamogetonaceae. 



saepe plus minus obovata vel spathulala, omnia stipulis liberis instructa. Caulis ra- 

 mosus vel subsimplex, fasciculis vascularibus in 1 — 3 partes confusis, in cortice fasci- 

 culis libriformibus subepidermalibus. 



A. Folia plerumque 1 — 2 cm longa. Fructus dorso dentatus 

 vel gibbosus vel basi tantum gibbis vel dentibus instructus. 



a. Carina media fructus band cristata (tantum dentata). 



a. Embryo curvatus vel hippocrepidiformis, nee spiraliter 

 involutus. 

 I. Folia natantia oblonga vel lanceolata. 



1. Fructus plerumque denticulatus raro basi tan- 

 tum dentatus. Folia submersa, flexilia nee 



rigida. 4. P. javanims. 



Conf. etiam P. variifolius (planta dubia). 



2. Fructus basi tantum 3 gibbis parvis. Folia sub- 

 mersa rigida 5. P asiaticus. 



II. Folia natantia lanceolata vel plerumque lineari- 

 lanceolata. Fructus dorso tridentatus, basi dente 



decurvato instructus 6. P. numasakianus. 



ß. Embryo spiraliter involutus, P. javanico similis . . 7. P. miduhilämo. 



b. Carina media fructus cristata 8. P. cristatus. 



B. Folia natantia minima, plerumque vix 1 ( — 1,5) cm longa. 

 Fructus dorso nee gibbosus nee dentatus. Folia submersa 

 uninervia. 



a. Folia natantia 5- vel plerumque plurinervia. — Species 

 americanae. 



a. Inflorescentia fruetifera fere reetangulari -lateralis. 



Fructus oblique obovatus 9. P. lateralis. 



ß. Inflorescentia fruetifera erecto - patens vel ereeta. 



Fructus rotundati-ovatus 10. P. Vaseyi. 



b. Folia natantia 3- (raro 4-[ — 5?]) nervia, plerumque 7 — 



1 mm longa. ■ — Species asiatica \\. P. limosellifoUus. 



4. P. javanicus Hasskarl in Act, Soc. Ind.-Neerl. V. |. (1856) 26; Schinz in 

 Ber. Schweiz. Bot. Ges. I. 60; Journ. of Bot. XXIX. (1891) 186; A. Benn. in Journ. 

 of Bot. XXIX. (1891) 122, 154; in Fl. capens. VII. (1897) 47. — P. heterophyllus 

 Harn, in Wall. Catal. (1828) n. 5181. — P. tmuieaulis F. Müll. Fragm. I. (1858) 

 90, 244, VIII. 2 17; Benth. Fl. austral. VII. (1878) 171; A. Benn. in Journ. of Bot. 

 XXV. (1887) 178; Morong in Bull. Torr. Bot. Club XIII. (1886) 158; Schinz ap. A. 

 Benn. in Journ. of Bot. XXVIII. (1890) 298. — P. parvifolia Buchenau in Abb. Naturw. 

 Ver. Bremen VII. (i 880) 32, 33. — P. Huülemis Welw. ex Schinz in Schweiz. Bot. 

 Ges. I. (1891) 61. — P. hybridus Hook. f. et Thoms. ex Schinz 1. c. (1891); Maximov. 

 Herb, ex A. Benn. in Journ. of Bot. XXIX. (1891) 122, 154 nee Mich. — P. oetan- 

 drus Herb. Beichb. ex A. Benn. in Annal. K. K. naturh. Hofmus. Wien VII. (1892) 

 288. — Caulis filiformis. Folia submersa pauca, anguste linearia ca. 1 mm lata, medio 

 nervis multis dichotome anastomosantibus reticulatis instructa. Folia natantia oblongo- 

 elliptica vel lanceolata, ca. 2—3,5 cm longa, basi angustata, paucinervia. Stipulae 

 tenues. Spicae densae, 8 — 15 mm longae. Fructus parvi, iis P. natantis minores 

 distinetius rostrati, semicordati, margine ventrali recto in apice suo stylum ca. 0,5 — 

 1 mm longum gerente, carinis saepe denticulatis. Embryo hippocrepidiformis. — Fig. 1 4. 



Afrika: Provinz Mossamedes (Welwitsch n. 248 ex Schinz, Schweiz. Bot. Ges.); 

 Kilevi am Kunene (Schinz n. 1001 !); Kunene (Baum n. 96!); Sudan (Schweinfurth 

 n. 1225!, 2909! ex Schinz 1. c. [1892] 154); Tiefer See bei Jeba (Barter n. 1069 

 ex A. Benn. 1. c. [1891]); Congogebiet (Pogge n. 1506!); Nyassa-See (A. Bennett 

 in Journ. of Bot. XXXIII. [1895] 138); Ostafrika (Stuhimann n. 1596!); Südostafrika: 



