102 



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



transformation of the tops of the secondary branches. Those buds break separately 

 when they reach their maturity. Moreover they are considerably larger and the lower 

 free leaves are similar to the other leaves of the branch. Cfr Hagstrom in Neuman, 

 Sveriges Flora 1901, p. 802—803. 



Very rarely there are turios on the rhizomes. As to their appearance it is 

 traced in fig. 39, D. 



Beside the main-form and v. minor Biv. Fischer has established two inter- 

 mediate forms: vulgaris and ndiliformis. Of var. minor he discerns four forms: ra- 

 mosus, squarrosus, flatycarfus and slenocarfus. Forma ligulifolius Fisch. is the form 



endowed with somewhat subcoriaceous invo- 

 lucral leaves. See Fischer, Die bayer. Pot. 

 1907, 109-110. 



A still more broad-leaved form than the 

 main-form I have found in some herbaria and 

 named 



f. austrinus n. f. — Folia latiora, 1,5 — 1,75 

 mm lata. 



This form is met with in' Africa. The 

 broad-leaved forms seem to spread southward 

 from the Mediterranean, and the narrow-leaved 

 to the north of it. 



Distribution. Stveden. Generally not 

 far from the Baltic and Bothnian coasts and 

 often in brackish water. Scania, Vegeholm, 

 88, Wallengren (hb. Uppsal.), Lund, 45, 

 L— M in hb. E. Fries (hb. Uppsal.), Ringsjon, 

 82, NiLSSON (hb. Lund., on a sheet together 

 with the hybrid P. imnorm. X pusill.). The 

 original Friesian specimen of P. gracilis from 

 Landskrona is not present in the Museums. — 

 Ostrogothia, Borensberg, Brunneby par., 73, 

 Bergstrom (hb. Uppsal.) Vreta, Berg, 88, 

 AuRELius (hb. Lund.), Takern, 83, Tollin (hb. Lund.), Linkoping, Kattbrunnen, 

 Sanden and others (hb. Uppsal. et Lund.), Grebo, Redinge, Sanden (hb. Uppsal.), 

 Norrkoping, 56, Hammarstbn (hb. Uppsal.). — Westgothia, Gothenburg, Kville- 

 backen, Lindholmen and Gullbergsvass, Lindeberg (hb. Gothenb.). — Stockholm, 

 Varmdon, Rorsundsvik and some other places (hb. Stockholm., Uppsal., Lund.). — 

 Sudermania: Igelsta in Hallsfjarden, 97, Hagstrom (hb. Hagstr.). — Oestricia, 

 Gefle, Hillevik in sinu maris, 47, Hartman, 35, Thedenius (hb. Uppsal.). — Medel- 

 pad, Skon, Fillan, 79, Seth (hb. Lund.). — Westbothnia, Ratan in aqua salsa, 68, 

 Krok (hb. Stockholm.). — Dalecarlia, Hedemora, 02, Tiselius (hb. Stockholm.). 



Norway, Flagsta-river, 88, Tiselius (hb. Stockholm.). — Denmark, Husum, 46, 

 Lange (hb. Uppsal.), Jutland, Nybro Kro, 96, Baagoe (hb. Uppsal.), Braband so, 



Fig. 39. P. pnKonnlfanus Biv. [j minor Biv. -4, By 

 Two tnrios, y, a, stem, b, leaf, //, tuiio, f, prophyllum, 

 /, scale-Ie.af. C, System of turios, nat. size, see the 

 text! Z>, Rhizomatic turios {h — //), y, 1, 2, 3, 4, inter- 

 nodes. E, Transverse section of a young ligule at the 

 middle showing the form and the bundles, '\'*, ic, front- 

 field, F, Young ligule, backfield-view, -j, showing the 

 top-form of the front-field and how far in some instances 

 the apical slit of the back-field can extend downwards 

 (dotted line). 



