178 



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



f. (or var.) lancifoUus Ch. & Schl. Both occur in rivulets. The same is the case 

 with V. pseudo-fhiitans Syme. — F. rotundifolius Fischer is probably the same as 

 ericetorum Syme. — If the f. cancellatus Fryer is not a hybrid, it might be consi- 

 dered a form of v. lancifoUus. Its short-petioled submersed leaves (Fryer, Pot. 

 Brit. Isles, 1898, 21, t. 12) make it a more dubious form. 



Distribution: P. polygonifolius occurs in many places of the Scandinavian 

 peninsula up to a line drawn from South Helsingland, Strakarra, the most northern 

 station in Sweden (coll. Zetterstedt, hb. Uppsal. et Lund.), through south Dalarne 



(Grangarde) to the middle of Vermland 

 (Rada, coll. Hagstrom, hb. Stockholm), 

 and from thence westward through 

 Nonvay, where it follows the western 

 coast to Sotith Nordland (Melo, 66° 50' 

 according to Blytt, Norges Fl. I, 1902, 

 46). Eastward it has spread to Alan- 

 dia (Geta, Svarttriisk, 01, Palmgrbn 

 & Klingstedt, hb. Stockholm.), but 

 is wanting in Oland and in Gothland, 

 and does not in the whole of Europe 

 transgress the 20tli degree east longi- 

 t>ide. From Europe it has spread to 

 the eastmost parts of Canada (New 

 Foundland and Sable Island to Nova 

 Scotia). From the above said north- 

 ern boundary, corresponding to the 

 year-isotherm of + 4 to +5 degrees, 

 it has ranged the whole of Europe and 

 northwestern Africa (Algeria, Morocco, 

 to Madeira and the Azores) reaching 

 the year-isotherm of + 20°, but surely 

 not much transgressing it. Specimens 

 from Madagascar held for P. polygoni- 

 folius are P. parmatus Hagstr. 



An Asiatic distribution-area is also 

 recorded (» Siberia altai (Led.) to Mon- 

 golia, and China to India and Japan » : Ar. Bennett, Pot. polygonif. in Bot. Gaz. 

 1901, 59. sSibirien bis Oatasien»: Graebner, Pot. 1907, 66). But I have seen no 

 specimens of true P. polygonif. from those regions, and the specimens recorded from 

 New Zealand may be the new species treated of here below. 



Fig. 92. P. poli/gonlfoltHs Pourr. A, Late in tlie year deve- 

 loped floating leaf from the top of a branch, j. B, Floating leaf of 

 the f. noroegicus Hagstr., -]. (7, Floating leaf of the f, juaderennia 

 Hacjstr., \. D, Part of a transverse section of the stem, ep^ epi- 

 dermis, /, lacuna, i, intercellular canal, /", strengthening lists, h, bast- 

 bundle, ^. E, Pistil, a side view, b back view, c, from above, 'i"- 



P. coloratiis Vahl. 



In HoRNEMAN, Flora Danica, 1813, t. 1449. 

 RoEMER et ScHULTES, Syst. veg. Ill, 1818, 504. 



P. plantagineus Du Croz ap. 

 P. lielodes Dumortier, Flor. 



