36 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE FOTAMOGETONS. 



The Canadian vaginatus constitutes a peculiar race: 



V. canadensis n. var. — Ligula paulo nervosior. Fructus latior, 2,3 — 2,5 mm (in 

 statu sicco), margine ventrali recto. — Anatomia caulis : cellulse epidermidis elongatse. 



The ligule has the same form with subretuse apex and the same length as in 

 the main-form, but is endowed with stronger nerves, by which, after the ligule has 

 decayed, the upper margin of the sheath gets another appearance than in the pri- 

 mary form. 



This variety stands to the main-form almost as the v. Macouni of P. filifonnis 

 to the main-form of this species. It is unlike inasmuch as the stem-anatomy also 

 deviates by its stretched epidermis-cells, and it may perhaps be necessary to sepa- 

 rate it as a distinct species P. canadensis, which I leave to future decision. 



The specimens examined are collected by Asa Geay, named P. pectinatus L., 

 mentioned in A. O. Kihlman, Pot. vag., in Medd. Soc. pro Fauna et Fl. fenn. 1888, 

 113, and by Macoun, near Banff in Alberta, Canada, 1891, named P. pectinatus Jj., 

 both preserved in the Univ. Mus., Christiania. Cypress Lake, Assiniboia, 95, Macoun 

 (hb. Haun.). 



Distribution. Sweden, West-Bothnia, Haparanda, 87, Hammaren (hb. Upp- 

 sal., Lund.), Skelleftea, Backfors, 75, Melander (hb. Stockholm., Uppsal.), Pitea, 

 Bredskiir, 69, Lundbbrg (hb. Uppsal.), Pitea, Recknon, 66, Lundstrom (hb. Lund.), 

 Umea, Tafle Skargard, 89, Andersson (hb. Uppsal.), Bygdea, Ratan, 68, Berg- 

 holm (hb. Stockh., Uppsal., Gotenb.), 1901, Fahlander (hb. Lund.). — Anger- 

 mania, Nora, Gronvik, 56, Fristedt & L^stadius (hb. Stockholm.), Sjalevad, 96, 

 Blomqvist & LuNDBERG (lib. Stockh., Uppsal.), Hernosand, 99, Tiselius (hb. Uppsal.). 

 — Medelpad, Tyndero, 88, Neuman (hb. Stockholm., Uppsal., Lund.), 91, Edvall 

 (hb. Uppsal., Lund., Gotenb.), 98, Lidholm (hb. Uppsal.). — Environs of Stockholm, 

 Stora Vartan, 46, J. E. W— m (hb. Stockh.), Viirmdon, Rorsundsvik, 88 & 96, Ti- 

 selius (lib. Uppsal., Lund., Got.), f. tenuior, Ulfsundasjon, 90, Ostling (hb. Stockh.), 

 in fresh water. 



Rorsundsvik at Stockholm is the most southern station on the Swedish coast, 

 59° 19' N. Lat. In Finland this species does not descend along the coast southward 

 farther than to 63° 30'. No specimen having been found between Stockholm and 

 Tyndero, the former place is to be considered as outside the proper distribution- 

 area, which may be reckoned to extend from 62° 30' northward. Following the year- 

 isotherm of this district of the Bothnian Gulf eastward, we arrive at the neighbour- 

 hood of Lake Baikal (Irkutsk— Selenginsk), see p. 33, above, and at Kamtschatka — 

 Aleutian Islands — South Canada. It is therefore probable that the Turczaninowian 

 habitat, Selenginsk, belongs to the south boundary line of the species, which may 

 fairly coincide with the year-isotherm for + 2° C. The particular distribution terri- 

 tory of P. vaginatus may be the large river-district of North Asia or the vast forest 

 territory of Siberia and northward up to the arctic regions (Tolstoi nos, Yenisei- 

 valley, 1876, Brekner, hb. Stockholm). From there it has spread eastward and 

 westward as is stated above. 



This supposition is confirmed by the records of the vegetation of Yenisei-valley 



