96 J. O. HAGSTEOM, CRITICAL EBSBAECHES ON THE POTAMOGETONS. 



— The colour of the leaves is always lively green, often with a yellowish tone, just 

 as in the foregoing and the following (P. fanormitanus) . 



Distribution. Sweden, not common. Scania, Rabelofsjon, 84, Tedin (lib. Lund.); 

 Kopingean, 76, Ljungstrom & Hxjmbla (hb. Stockholm, Uppsal., Lund.); Hoj, hb. 

 E. Fries (hb. Uppsal.); Hojea, hb. Ag. (hb. Lund.); Lillsjon at Krageholm, Duben 

 (hb. Lund); Malmo in the channel at the railroad, 61, C. A. W. ; Vejle lake, Dtjben 

 (hb. Lund.), 81, Wallengren (hb. Stockholm.); Nybro, 08, Jonsson (hb. L. M. 

 Neuman). — Ostrogothia, Roxen (hb. Stockholm.). — Gothland, near the church of 

 Sanda, 53, Westoo (hb. Uppsak). — Sudermania, Eskilstuna, Hn. (hb. Stockholm.). 



— Stockholm, several stations (hb. Stockholm., Uppsal., Lund., Gothenb.). — Ufp- 

 land, Skeboan, 67, Mosen (hb. Uppsak, Lund., Gothenb.); Satuna, 46, Afzelius 

 (hb. Uppsak, Lund.); Metsjon, 81, Tiselius (hb. Stockholm., Uppsak); Tranbygge 

 mill-river, 81, Tiselius (hb. Stockholm., Uppsak, Lund.); Valloxen, 81 Tiselius (hb. 

 Stockholm, Uppsak, Lund.); Sigtuna, Viby, 80, Floderus (hb. Uppsak); Norrtelje- 

 viken (hb. Stochholm.); Uppsala at Falebro, 20, hb. Wahlenberg (hb. Uppsak); 

 River at Haga, 51, Zdt (hb. Uppsak). — Gestricia, Gefle, the south Lilla, 48, Hart- 

 man (hb. Uppsak); Islandsan, 64, Thedbnius (hb. Stockholm, Uppsak); River at the 

 southern wharf, 35, Thedenius (hb. Uppsak), f. borealis m. — Helsingland, Soder- 

 hamn, 47, Svedberg (hb. Uppsak), the most northern locality of Sweden, on 61° 15' 

 lat. bor, 



Norway, Drammen, Blytt in hb. E. Fries (hb. Uppsak); Skien, Blytt (hb. 

 Uppsak). — Denmark, several stations (hb. Stockholm., Uppsak, Lund.). — Finland, 

 Alandia, Geta, Bolstaholm lake, 01, Palmgren & Klingstedt (hb. Stockholm.). 



— Germany, several stations in Silesia, Brandenburg and Holstein (hb. Stockholm., 

 Lund.). — England on several stations (hb. Stockholm.). 



North America, Manistee, Mich., 80, Hill (hb. Stockholm.); Perry, N. Y., 82, 

 Hill, and Geneva, N. Y., 84, Morong (hb. Stockholm.); Nov. Angk, Tuckerman 

 (hb. Uppsak); Aux Bees Scies, Mich., 80, Hill (hb. Stockholm.); Hastings County, 

 Canada, 74, Macoun (hb. Stockholm.). The northern limit of this species in Europe 

 and America may be the year-isotherm of + 4° C. How far to the south it extends 

 is not fully known, at the most to the j'^ear isotherm of + 15° C, or perhaps rather, 

 + 12° C. 



P. miicroiiatus Schr. x obtiisifoliiis M. & K. (P. semifriictiis Ar. Bennet 

 ap. Gr^bner, Potamogetonacese 1907, 138, nomen solum; Asch. & Gr., Syn. mittel- 

 eur. Fk, 2 Aufl. 1913, 535, as obtusijol. X Friesii?). 



In Dr. C. J. Hartman's herbarium (hb. Uppsal.) I have found some specimens 

 which must be referred to this hybrid. The leaves are in general like those of 

 P. obtusifolius and brown-coloured, but part of them have the apex of a mucronatus- 

 leaf. Ligules greenish and bicarinated as in P. mucronatus. 



Other specimens, collected by J. H. Wallman at Linkoping and by E. Fries 

 in Herb. Norm. V, 81 distributed under the name of P. obtusifolius v. lacustris, have 

 an unusual scarce ramification, especially in the spike-region, lighter colour shading 



