224 



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



f. 



LfBstadii n. f. - 



f. 



subovalis n. f 



f. 



brevior n. f. 



Folia caul. subm. elongata basi subcordata, 100— 120 X 15 mm. 



— Folia caul. subm. basi ovalia subcordata, 45— 60 x 10 — 11. 



— Folia caul. subm. brevia, basi subcordata— cordata, 35—45 



X 10—12 mm. 



f. restrictiis n. f. — Folia caul. subm. 

 parva, 20 x 6 mm, basi rotundata. 



Habitat: N. America, see below ! 



f. stenobasis n. f. — Folia caul. subm. 

 basi lanceolata, spathulata, 50 X 7 — 8 mm, 

 vel supra. 



This rare form has narrower leaf- 

 basis than all the others and can easily 

 be mistaken for pure P. gramineus or 

 the hybrid P. Zizii. It is distinguished 

 by the leaf-apexes and the stem-ana- 

 tomy etc. 



At last I should remark that, like 

 P. gramineiis, almost each of the different 

 crosses seems to be able to produce 

 terrestrial forms with more or less coria- 

 ceous leaves (f. ierresiris Fries, Nov. 

 Fl. Suec. 1828, 35. — Tiselius, 1. c. 

 nos. 44, 142, 143). 



p subperfoliatus (Ratjnki^r) Hagstr. 



f. imclongifolius (Tis.). P. nitens (3 

 prcelongifolius major Tis., 1. c. n:o 45. 



Stem-leaves with broadly cordate 

 rounded base 120— 150 (170) X 20 (.30) 

 mm. Topmost leaves, on the stem 

 prolongation, rarely with stalk-like base; 

 internodes usually very long. 



This beautiful plant is a true 

 nitens {gramin. X 'perfoliatus)-ioTm and 

 . J'!-. "I' "''" r""'" ^™- "■ ™''»'-«'""'f« (Eaunk.) Hagste. presents no influence from P. pro'lonqus. 



A, Uabit-picture showing the primary and secondary involucral ^ . 



leaves, |, a, primary spike. B—H, Submersed stem leaves, -}, B, It COincideS witll, Or is at Icast UlOSt 



t. invohitns ¥nYEu; C, {. Licstadil H/lgstk., D, t. siibomlis Uaqstr., ,., ^ ,..,,. ,^, j. , 



E, f. brevior Haostk., F, f. stenobasis Hagste., G, f. restrictiis ilkC P. SallClJOilUS WOLFG. aCCOrding tO 



Hagste., H, f. innomitiatits (Tis.) Hagste. ji t • j.- n „„ : „„ 



^ ' the description as well as specimens 



gathered and determined by Wolfgang himself and labelled: »P. salicifoliiis mihi 

 e fluvio Wilia Lithuania J. W.» »Mis. Wolfgang* (in lib. Petersburg). The same 

 plant is the »P. salicifolius Wolfg. In fluv. Willia Lithuan. Herb. W. Bessbr» ex 

 »Herb. Ledeeour» (lib. Petersb.). Besides, I have seen the same plant from the »Herb. 

 Musei Palat. Windob.» 



