KUNOL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 143 



leaves 15—20 mm. broad. The rivulet-form of this, with often greener leaves, is 

 var. rivularis Hartm. Var. palustris M. & K. is a form with very short internodes, 

 and f. brevifolius Tiselius has shorter leaves than usually, ^-15 mm - Forma lo?igi- 

 j olins L^estadius has elongated leaves 150 X 10 — 15 mm. Forma minor Hartm. origin- 

 ally seems to have been the same as f. angustifolius Cham., but became defined in 

 Handb. i Skand. Fl., 1820, as a form »till alla delar dubbelt mindre» i. e. in all 

 parts only the half of the main-form (=f. borealis Tis.). Var. lacustris Marsson is a 

 narrow-leaved form with elongated internodes (=f. gracilior Tis.). I have observed 

 a narrow-leaved extreme form with only 5—6 mm broad submersed leaves which may 

 be named: 



f. gracillimus n. f. — Fo.lia submersa 5 — 6 mm lata. 



All more narrow-leaved forms may be united under a common variety-name: 



var. linearifolius n. var. — Folia submersa angusta lanceolate-linearia 100 X 5 

 —8 mm. 



This var. thus comprehends ff. minor Hn, lacustris Mars. (gracilior Tis.) and 

 gracillimus Hagstr. 



A broad-leaved extreme form I have named: 



f. ovatifolius: folia submersa 70—80 mm longa, 35 mm lata. 



All forms destitute of floating leaves in proper sense constitute the var. obscu- 

 rus Asch. 



The Fieberian exposition is maintained by Fischer in his work Die bayer. 

 Pot. in 1907, where several new forms have been established and earlier names have 

 obtained a new meaning. 



Distribution. Sweden. P. aVpinus occurs through the whole of Sweden from 

 Scania as far as the most northern parts of Lapland, and plenty of materials from 

 all counties except Oland is deposited in the Museums. F. gracillimus is known 

 from two localities: Westgothia, Släpsjön, 87, Nordstedt (hb. Lund) and Herjedalia, 

 Lillherdal, 01, Enander (hb. Stockholm, et Lund.). 



Other northern habitats are: Norway, many stations, Iceland, Greenland, Russ- 

 ian Lapland, Varsuga, 89, Kihlman (hb. Stockholm.) Voronisk, 87, Kihlman (hb. Stock- 

 holm.). Siberia, recorded by Scheutz, Planta? vase. Jeniseenses from small lakes in the 

 region of Dudino, 69° 25, N. L. It occurs also in a lake in the Laostrovskoje island, 69° 

 45, N. L. (hb. Stockholm.) and, consequently, transgresses the year-isotherm of - - 10° C. 

 — In N. America, however, it may not reach this line. Robinson & Fernald in 

 Gray's New Manual, 1908, record: Labrador to Alaska, and the author has seen 

 specimens from Yukondistrict coll. by O. Nordenskjöld 1898 (hb. Stockholm.). 

 The northern boundary of this species, therefore, may be the year-isotherm of —6° 

 to — 10° C. To the south of this line it spreads through Europé, Asia and North 

 America, but surely not much beyond the year-isotherm of + 15° C. Asiatic state- 

 ments from the south of this line may be referable to P. stylatus Hagstr. (Bot. Not., 

 1908). It is not at all probable that it in Asia transgresses the European south 

 boundary, rather the contrary, on account of the high summer warmth. 



DpMmark and Germany: a great many specimens are present in the Swedish 



