72 



J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



[Ti 



coll. J. A. Holm) is misreported by E. Collinder, Medelpads Flora, 1909, 179. The 

 plant referred to is P. zosterijolius, which has spread more northwardly (see p. 66). 

 On the west coast a single station is recorded, viz. Oothenburg, 53, Krok, Lindbeeg 

 and many others in later times (hb. Stockholm., Uppsal., Lund, et Gothenb.). 



The statement from Nonvay (Skien) Blytt, Norges Flora I, 1861, 368, is a 

 mistake instead of P. mucronatus (see under that species!) according to Blytt's 



examples as well as A. Blytt, 

 C Z;^ Norges Flora I, 1902, 49. The 



northern limit of P. acutifolius 

 in the Scandinavian Peninsula 

 thus runs from Orbyhus (Upp- 

 land) to Orebro {Nericia) and 

 Gothenburg. The species, how- 

 ever, does not appear equally scat- 

 tered over the whole area to the 

 south of this line, but in three 

 isolated small districts: 1) a west- 

 ern one: Gothenburg, 2) a south 

 area: Scania with south Halland, 

 and 3) a northern, larger district. 

 The stations within this last one, 

 strange to say, seem to be situ- 

 ated on the old bottom of the Li- 

 torina Sea. Hence we might per- 

 haps suppose P. acutifolius to be 

 a rather recent plant-immigrant 

 to Sweden. 



Extra-scandinavian stations : 

 ,„„,.„ „ „ .„ ^ , Denmarh, near Copenhagen etc. 



Fig. 28. A — E, P. sudevmaniciis Hagstr., is P. pusilhis L. — yl, ' x o 



Basal portion of a stem-leaf, V; -S, Transverse section of a stem-leaf at (hb. Stockholm., XJppSal. Ct Lund.). 



the middle, '^^ , m, midvein, 71', lateral nerves, Z, lacnuar system, sty, ^ , . /-Ul, 



mechanical strands, the marginal bundle very strong; C, Transverse sect, \:r P.TlTlCtl'iy ^ SCVCral plaCCS (HD. 



of the stem, ^{"^ cc, central axis, sir, subepidermal strands; D, Longitudinal Qf r^/^lr-hrilm TT-nt-iaQl t^f T itnri ^ 



section of the epidermis, Y; -'?. Transverse sect, of the peduncle, »^, showing iJtOCKllOim., Uppsai. GZ LiUnU..). 



.two median (vh) and two lateral vascular bundles and a single subepidermal FfdnCC SCVCral "OlaceS (lib 



bast-bundle. — F, Basal parts of stem-leaves, a, snbpetioled, h, sessile, ^^, ' ir \ ' 



Stockholm., Uppsal. et Lund.). 

 From those countries as a centrum it seems to have spread to Bohemia, in lacu 

 Zaklici, Velenovsky (hb. Lund.), Transylvania prope Baumgart, Dr. Schur (hb. Stock- 

 holm.), Belgium (hb. Uppsal.) and England, Middlesex, Linton (hb. Uppsal.), Nor- 

 folk, 87, Bennett (hb. Stockholm, et Uppsal.). It is also recorded from Russia, 

 Plescau, and Italy, but I have not seen specimens from thence. Australian and 

 Manchurian plants referred to P. acutifolius surely are something else. 



P. acutifolius, thus, has a comparatively limited distribution-area, and is toge- 

 ther with P. coloratus an almost exclusive European species. 



