236 



,T. 0. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGBTONS. 



Fig. 110. A — C, P. liicens 1j. J, Leaf-margin, 

 showing the denticulation and the sinns between 

 two denticles, enlarged, li, Transverse section of 

 part of the ligale at the base, -y'*, showing the 

 structure and the height of the ridge in relation 

 to the thickness of the intercarinal part, ic, F, 

 and G, corresponding parts of P. grainineus X 

 Incens {P. Zizil M. K.) and P. gramhlens L. to 

 show the intermediate position of the former. C, 

 Pistil, a, side-view, b, stigma from above, \^. D 

 — E, P. lucens L. v. longifolius DC. Z>, Basal and 

 apical part of a stem-leaf, -|. E, Basal and apical 

 part of a branch-leaf, -J-. F, P. graminetis X Incens 

 (P. Ziz'tl M. K.), transverse section of ligule, as 

 in B, \°. G — H, P. gyamineiis L. 6', Transv. sect, 

 of ligule. as in B, '/'• I'lie dotted line indicates 

 the height of the ridge at the involucral leaves. 

 //, Leaf-margin, showing the denticulation, enlarged. 



LoEW, ScHROTER, Lebensgesch., 1906, 450, f. 254: 

 hybernating forms. — Fontell, Beitrage etc. 1909, 

 t. Ill, f. 80—83, t. IV, f. 90-91: anatomical 

 pictures of stem, rhizome etc. 



Distribution. Sweden, Scania and through 

 the whole country (hb. Stockholm., Uppsal., Lund., 

 Gothbg.) as far as Helsingland, Jerfso, Kalfsjon, 89, 

 ScHLYTER (hb. Uppsal.), Medelpad (the valley of the 

 Ljungan and the Giman) Borgsjon, 04, RiNGius (hb. 

 Lund.), Torpsjon, 60, C. Rn (hb. Uppsal.), f. insignis, 

 Stodesjon, 05, Collinder, Mellansjon, 10, Nord- 

 strom, and East Jemtland, Holmsjon, 84, Tiselius 

 (hb. Stockholm.), Hallesjo, Hasjo, 64, Tiselius (hb. 

 Stockholm., Uppsal., Lund.) and Hasjo — Ragunda: 

 Mill-lake, 86, Sundberg, the most northern station 

 of Sweden, ca. 63° n. lat. with a year-isotherm of 

 about + 3° C. Consequently it is not observed in 

 Western Jemtland, Herjedalia, Western Helsingland, 

 West and North Dalarne and Wermland. 



Norivay, Hsersoen, Blytt (hb. Uppsal.), 

 Asker, Hogstadtj. and Padderudsv., Hadel. (Jaren), 

 Hedem. (Stavsjo); besides in Jsederen, Soglandsv. (hb. 

 Christian.). — i'^m?a«d,Tavastiaaustr., Rauntunselka, 

 83, Granberg (hb. Stockholm., Uppsal., Lund.). 

 The statement in Hjelt & Hult, Vegetationen o. 

 Floran i en del af Kemi Lappmark etc. in Meddel. 

 Soc. Fauna et Flora fenn. XII, 1885, that P. lucens 

 occurs at Kolari, is no doubt a mistake (probably 

 for P. gramineus f. septentrionalis Tis. (Hagstr.)). 

 P. lucens is a much more southern species than P. 

 gramineus. — In the Swedish Museums there are 

 a great many specimens from Denmark, England, 

 France, Germany, Austria — Hungary, Stvitzerland, 

 Italy, Venetia, 78, RiGO (hb. Lund.), Hercegovina, 

 89, MuRBECK (hb. Stockholm., Uppsal., Lund.). 

 Lithuania, Vilna (hb. Stockholm., Uppsal., Bremen.), 

 V. longifolius: — Has long internodes and short 

 branches; stem-leaves narrow and protracted 200 

 — 350 X 15 — 20 mm, short-petioled (10—20 mm) and 

 with rather weak serrulation (foliis integerrimis: 

 WoLFG., is misleading), their ligules 70 — 100 mm 



with 



more 



long; branch-leaves 

 or less abruptly cuspidate apex, see 



the figure 



likewise 

 110, 



narrow, 12 — 15 mm, 

 tapering base, short 



