70 P- Graebner. — Potamogetonaceae. 



Lusus subspathaceus Aschers, et Graebner 1. c. (1897). — P plantagineus 

 subspathaeeus Reichb. Ic. fl. germ. helv. (1845) t. XLV, fig. 84. — Folium spathaceum 

 6 mm longum et 5 mm latum basi spicae affixum. 



Nota. Haec species saepe (etiam ab cl. Hornemannio et G. F. W. Meyero) cum 

 P. polygonifolio mixta est, sed plerumque foJiis natantibus membranaceis et fructibus parvis 

 leviter differt. 



Subsect. 6. Alpini. 



Alpini Graebner. — Conf. p. 41. — Folia submersa inferiora sessilia, superiora 

 tantum petiolata natantia vel submersa, rubentia. 



A. Folia submersa (superioribus tantum interdum exceptis) semper 

 sessilia. 



a. Folia submersa plerumque lanceolata, natantia obovata 



vel oblongispathulata coriacea 36. P. alpinus. 



b. Folia submersa plerumque late linearia vel sublanceolata, 



natantia spathulati-lanceolata, vix coriacea 37. P, Griffithii. 



B. Folia submersa (an in P. linguato etiam inferiora?) petio- 

 lata. — Species americanae vel Asiae orientalis. 



a. Folia submersa obtusa, tenuia, natantia coriacea, ovali- 

 subcordata. Fructus ca. 3,5 — 4 mm longi, dorso cari- 



nati. — Species patagonica 38. P. linguatus. 



b. Folia submersa acuta (interdum obtusa) plerumque 3 — 

 1 3 nervia, plerumque 3 — 13 cm longa, natantia nume- 



rosa coriacea. — An Hybrida? boreali-americana . . . 39. P. Faxonii. 



36. P. alpinus Balbis in Act. Jurin. X. XI. (1802 — 3) 329 emend. Aschers. Fl. Prov. 

 Brandenburg (1864) 658 ; Aschers, u. Graebner, Synops. mittelem*. Fl. I. 311. — P. serra- 

 tum Roth, Beitr. II. (1783) 126? conf. A. Bennett in Journ. of Bot. XXVIII. (1890) 298. 



— P. fluitans Smith, Fl. Brit. (1800 — 1804) 1391 nee Roth. — P fluitans Schumacher 

 in Hörnern. Fl. Dan. (1813) t. 1450. — P. spathulatus Schrad. in Koch et Ziz Cat. 

 PI. Palat. (1814) 18? ex A. Benn. in Journ. of Bot. XXVII. (1889) 243 XXX. (1892) 

 conf. P. alpinus X polygonifolius. — P. semipellucidiis Koch et Ziz, Cat. pl. Palatinat. 

 (18 15) 5, 18. — P rufescens Schrad. in Cham. Adnot. ad Kunth, Fl. berol. (1815) 5; 

 Cham. u. Schlechtd. in Linnaea II. (1827) 210; Koch Syn. ed. 2. (1844) 777; 

 Reichb. Ic. fl. germ. helv. VII. t. 32, fig. 56—58; A. Bennett in Journ. of Bot. XXV. 

 (1887) 372, XXVIII. (1889) 242. — P purpurascens Seidl in Presl, Fl. Öech. (1819) 

 25 emend. Fieber, Potam. Böhmens (1838) 16. — P lucens var. angustifolius 

 Hörnern. Fl. Dan. (1819) t. 1635. — P microstaehys Wolf in Roem. et Schult. 

 Mant. III. (1827) 359 sec A. Benn. in Journ. of Bot. XXV. (1887) 372? cf. autem 

 t. XXIX. (1891) et inter varietates. — P nigrescens Fries, Mant. III. (1842) 17. 181. 

 Laestadius in A. Bennett in Journ. of Bot. XIX. (1881) 66. — P oblongo-rufescens 

 F. Schultz, Flora XXXII. (1849) 230? ex A. Benn. 1. c. 244 conf. P alp. X polyg. — 

 P. Koehii F. Schultz, Arch. Fl. France et Allem. (1842—54) 72. — P lucens var. 

 rufescens Benth. Handb. Brit. Fl. ed. 1. (1858) 493. — P alpino-natans F. Schultz 

 in Jahresb. Pollichia (1863) 229? — P obtusus Wood ex A. Gray, Man. North. U. 

 St. (1868) 486. — P lanceolatus Du Croz ex A. Bennett 1. c. XXV. (1887) 372; 

 Hook, ex pte. sec. A. Benn. 1. c. (1889). — P retusum Sm. sec. A. Benn. 1. c. XXV. 

 (1887) 372 et 1. c. (1889). — P lucens Lagasca ex pte. sec. A. Benn. 1. c. (1889). 



— P Thomasii Herb. Wien ex A. Bennett in Annal. naturhist. Hofmus. Wien VII. 

 (1892) 288. — Rhizoma repens, plerumque ramosissimum, plerumque rufescens vel 

 roseum. Caules plus quam 2 m longi, sicci saltem rufescentes. Folia omnia integra, 

 immersa lanceolata, basi et apice dilatata, ca. 25 cm longa et 2,5 cm lata, obtusa, 

 nervis medianis distinete reticulatis, natantia coriacea obovata vel oblongi-spathulata, 

 in petiolum quam lamina breviorem attenuata. Stipulae ca. 6 cm usque longae, robustae, 



