KUNGL. SV. VET. AKADEMIEKS HANDLINGAR. BAND 55. N:0 5. 209 



Russia, Lapponia ross. Nuortijaur, 83, Hollmén (hb. Stockholm., Uppsal., Lund.), 

 f. seplentrionalis and i.Wolfgangii ; Karna, 64, Andersson (hb. Stockholm.), v. lacuslris; 

 Dnjeper prope Kiew, 09, Lonatschewskij (hb. Stockholm.). - - Iceland, Hof i Vatnsdal 

 (hb. Lund.); Reykiavik, 76, Grönlund (hb. Uppsal.). - Faroe Islands: Suderö 

 (hb. Stockholm.), f. terrestris. - - The northernmost boundary of this species seems 

 to coincide with that of P. natans, but it does not spread so far to the south at 

 all. The southern limit may be about the year-isotherm of + 16° C or a little beyond. 

 Traces of a south Italian occurrence, see under P. gramineus xlucens, p. 215! 



Some English forms from Cambridgeshire and Huntingdonshire gathered by A. 

 Fryer (hb. Stockholm.) and sometimes labelled as P. varians Mor., sometimes as 

 P. jalcatus Fryer etc. are mostly pure P. gramineus f. nigrescens Fries, sometimes 

 verging to f. jemtlandicus Tis. and f. Wolfgangii (Kihlm.). The fact that the submersed 

 leaves are sometimes large (100x8—13 mm) ought to be ascribed to the ground 

 conditions (growing on peat: Fryer). So for instance some specimens from Grunty 

 Fen (n:os 1732, 2243, 1277), pure f. nigrescens; likewise n:os 2056, 2057 from Block 

 Fen, Chatteris, labelled »Potamogeton spathceformis Tuck? = Zizii X Jieterophyllus 

 varians major?»; and n:o 2054 from Witcham Meadlands, Mepal, labelled: »Potamogeton 

 varians Morong ! Specimens from this locality were sent to Dr. Morong and named 

 varians by him. This is the typical English form described in The Journal of 

 Botany», and many other specimens from the same station are f. nigrescens (with 

 transitions to f. jemtlandicus); n:os 2156 and 2160 (same locality) is P. Zizii or 

 sooner gramineus X Zizii. Huntingdonshire, Stocking Fen, Ramsay, 89, Fryer n:os 

 1265, 1275, 1086, labelled »Potam. jalcatus Fryer» are true P. gramineus verging 

 to f. jemtlandicus Tis., or f. nigrescens Fr. — Further on P. jalcatus, see under X 

 P. nitens, p. 231! 



Asia. Siberia, Yenisei, Vorogova, 76, Arnell (hb. Stockholm., Uppsal.), terr. 

 silv. in lacu minore, the main-form, year-isotherm — 5 C C. Ob, 66° 46' lat. bor.. 80, 

 Sommier (hb. Kristiania), f. Wolfgangii. Pamir, 98, Paulsen (hb. Haim.). 



N. America. Brit. Columbia, 89, Macoun (hb. Stockholm.), Manitoba, 96, 

 Macoun (hb. Kristiania). Northern U. S., many stations (hb. Stockholm., Uppsal., 

 Kristiania). Besides the main-form, I have seen the f. jemtlandicus from N. Ebor., 

 Tuckerman (hb. Uppsal.) and from Idaho, 92, Mc. Dougal (hb. Stockholm.), f. 

 Wolfgangii (Kihlm.) from N. Angl, Tuckerman (hb. Uppsal.), f. nigrescens from 

 Mass. and Mich. (hb. Stockholm.), and v. myriophylliis from locus classicus, Apponang 

 Pond, Rhode Island, 81, Morong (hb. Stockholm.). — Greenland, Julianehaab, 83, 

 Nathorst (hb. Uppsal., Lund.), Igalito, 47, Vahl (hb. Stockholm., Uppsal.). Also 

 in N. America the species may occur between the year-isot herms of - - 5° and -f 18° C. 



P. gramineus L. x illinoensis Mor. (P. deminutus n. hybr.). 



Folia superiora late et obtuse cuspidata more P. illinoensis, submersa breviter 

 petiolata— subsessilia, fuscoviridia. Ceterum in omnibus fere partibus etiam in ana- 

 tomia caulis planta medium inter parentes tenens. 



K. Sv. Vet. Akad. Handl. Band 55. N:o 5. 27 



