KUNGL. SV. VET. AKADEMIENS HANDLINGAB. BAND 55. N:0 5. 19 



Lund., Gotenb.), Klinte, 72, Zetteestedt (hb. Uppsal., et Lund.); Oland, Alvaret, 

 Resum, 03, Witte (hb. Uppsal.); Smoland, Vastervik, Granso, 63, C. F. W. (hb. 

 Stockh.) Westgothia, Floby, 93, Stenholm (hb. Lund.). — Norivay, Jsederen, 84, 

 MuRBKCK (hb. Stockholm, et Uppsal.), Laurgard, 68, Nobdstedt (hb. Lund.), Por- 

 sanger and several other stations (hb. Christian.). — Denmark, Jyll., Ravnstorp aa, 

 Viborg, 70, Nielsen (hb. Uppsal.). — Switzerland, Lac Doniene, Alpensee im Canton 

 Freiburg, D:r Lagger (hb. Uppsal.). — Bavaria, in rivulo Ramsach prope Murnau, 

 05, G. Fischer (hb. Stockh.), by Fischer labelled: "Potatnog. juncfoliius Kern. ». 



Var. C libetanus Hagstr., Potamog. from Asia in Bot. Not. 1905, 124: — i^oZia 

 linearia (%— 1 mm), sequali fere latitudine usque ad apicem, apice breviter rotundata 

 vel ssepe triangularia; vaginae 20—35 mm longse. — Very much like the preceding 

 var. but with longer sheaths. Anatomy of the stem is the same. Fruit as usual. 



Occurs in Asia, N. Tibet, Upper Kum-Koll, Dr. S. Hedin (hb. Univers. 

 Stockholm.), Tibet occ, Thomson (hb. Stockholm.). — The form, mentioned by 

 J. Baagoe in Potamog. from Asia-media, 1903, 183, n. 11 from Pamir, Bulung Kul, 

 alt. 3,800 m, is also the present variety. — Fig. 4, H. 



P. filiformis seems to be principally an alpine and northern species. After 

 the glacial period it evidently has spread northward from especially three sources: 

 1) The German Jura through Germany to the Baltic and surrounding countries, 

 and northwestward to England, Shetland etc., Faroe Islands, Norway (to Magero, 

 hb. Christian.), Iceland. 2) High-Asia, how far to the north (northwest and north- 

 east) is not fully explored. The author has seen specimens from Siberia, Vorogov in 

 Yeniseivalley at 61° n. lat, coll. by M. Brenner (hb. Stockholm.). 3) Rocky 

 Mountains to Wyoming and Nevada (var. occidentalis Robb.) — Northeastern United 

 States and Canada — West-Greenland to Disco Island, near Narsak, 71, Fries (hb. 

 Uppsal.), and Omenak Fjord, Ikerasak (ca. 71°), 92, Vanhoffen (hb. Hauniense), 

 probably the most northern place hitherto known. 



To the south of the line of The Pyrenees — The Alpes — Himalaya it seems not 

 to have spread. At least we know of no sure statements. The report of Au- 

 stralian habitats may need further confirmation. But that line coincides nearly 

 with the year-isotherm for + 15° C, and it is rather certain that the species does 

 not surpass this line in America either. Thus we should have its occurrence between 

 the year-isotherm of + 15° and — 5° (Omenak) to 8°, in Siberia up to — 10° C or more. 



As to Sweden it is not very rare in bays along the Baltic coast. — In fresh 

 water it occurs chiefly on calcareous ground. (Gothland: Tingstade, Oland, Scania, 

 Ostrogothia: Lake Vetter, Westgothia, Upland: Lake Maelar, etc., Jemtland and 

 Lapland: Barrseleavan). The museums include a great deal of material from all 

 these counties. ■ — • On the west coast of Sweden it is found only at Otteron in Ba- 

 husia (immigrated from Norway?). 



Finally I will point out the biological conformity that is to be found between 

 the most northern forms in Greenland and the forms in the Alps and High-Asia 

 (Thibet), namely the longer sheaths (f. polaris and f. tihetanus), evidently an adaption 

 to colder water. 



