232 



J. O. HAGSTROM, CR1TICAL RESEARCHES OX THE POTAMOGETOKS. 



Habitat: Siveden, Smoland, Ålem, Strömsrum in fluvio Alsterån, 96, H. Rappe 

 et H. Tiselitjs; Tveta in rivö Emån, 1862, Johansson (hb. Uppsal.). 



Another form is found in Scania with more gramineus-Yike lower 

 leaves: 



p SubcuspidatllS n. f. Folia submersa inferiora sessilia ut in P. grä- 

 mt neo apice subcuspidata, superiora petiolata summa coriacea basi sa?pe 

 subcordata; ligula? caducae; spica major ut in P. gramineo. 



The colour of this form is like that of P. polygonifolius. Both forms 

 accord with each other as to the ligules, the non-serrulate leaf-margins and 

 the nervation, non-incrassate peduncles, and in the complete sterility. The 

 stsm-anatomy also corresponds very nearly: P. gramincus generally pre- 

 dominates in the periphery, polygonifolius again in the central cylinder. 

 Consequently we always find cortical and subepidermal bundles as in the 

 former, but tvvo median xylem canals and more or less free lateral bun- 

 dles in the stele as in the latter. Endodermis of »-cells, intermediate. 



Habitat: Siveden, Scania, Pinneå, 1911, L. M. Neuman. 



The plants described above do not coincide with a plant from Bor- 

 kurn preserved in the Berlin Museum, gathered by O. v. Seemen and la- 

 belled »P. polygonifolius X gramineus. P. Seemenii.» »P. Graebner det. » 

 »Herb. P. Ascherson.» The hybrid nature of this plant is not quite cer- 

 tain, as all its pollen is fresh and fertile. At an}' råte it extremely ap- 

 proaches to P. gramineus: Leaf-margin serrulate (ca. 10 teeth a cm), apex 

 acute, branch-leaves — like the lower stem-leaves — sessile, style and anatomy 

 of the stem like those of P. gra/min. ()n the other hand the upper nar- 

 row leaf-bases and the narrow pedunele are reallv a little stränge to P. 

 gramineus; but the specimen is also a late flowering autumnal shoot 

 (gathered 23. Vill, with fresh pollen!), from which no certain conclusions 

 can be drawn. Be this as it may, the name P. Seonenii must stånd for 

 t lic hybrid P. gram. :< polygonif. {polygonif, x gram., ex Graehn.). 



A dubious plant from Scotland, gathered by F. COLBS is also pos- 

 Fig. 109. p 8 j D ly this hybrid. No other localities are hitherto known. 



gramintus X 

 polygottifclin» 



( /'. St ■■ii" nii A. 

 •^ Bb.). .1. i 



Inur. olatifo- 

 II- liv.. 



äubmei 



■ • . i • ". 

 heutpidw 



TopoSyonn^ i'» Haetm., Ilamlb. Skaud. FL, ed. 12, 1SS9 p. 49, P. Lundii RlCHT., Pl. 



:""' Kur. 1, 1S90, L3, qui est /'. gramin.X perfol. (/'. nilens WEB.) v snbinhr- 

 medins HaGSTR. f. tnirlarcn 9tS Tis., vide supra, ]). 226.) 



Habitu el colore P. prcelongo similis. Folia ramea superiora parva, basi lan- 

 ceolata vd brevisnme Iateque petiolata; omnia margine integerrima apice oavi- 

 cularia. 



In lss<> S. Almquist (/. c.) relätes <>t' a Potamogeton Ironi »Ö.Sm., Vimmerby, 



P. gramineus L. prtelongns Wulp. 



(/'. narindnris n. hybr., non /'. gr amin. ".< prodongué ex ALMQUIST 



