32 



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



nical strands both on the upper and lower surface and in addition 1—2 över the 

 midrib (fig. 10, B). In this manner the leaves become a little striate. Counting 

 also these faint nerves, the leaves appear 7 — 9-ribbed. 



The verticils closely placed at regular intervals suggest in this species an ob- 

 vious affinity to P. vaginatus. The characteristic apex of the involucral leaves 

 resembling that of the Callitriche vernalis (possibly only a secondary formation) and 

 the bifurcate fruit make it easily distinguishable from all the other Coleogetons. 



Distribution. Siberia, Yenisei, Nikandrovskij-island, 1876, M. Brenner (hb. 



Fig. 11. /'. vaginatus luncz. .1. Top of a stom-leaf, ef. the mxt tig. /.'.', \-. /', and C, Tops of branoh-leaves, y. /), I.eaf- 

 axil ainl raniilication (natural size, but for butter illustration BOmewhat sohematizod), a, niain-shoot benoatli the miildle, b, leaf 

 with sheath and ligulo {rj clasping tbo basal parts of four evolved brancbes of 1st to 4tb rank (/, 'J, 3, 4) and a small bud 

 ( I of Mh rank, f, prophyllum, /, BCale-leaveS, from whioh tbo brancbes 2, 3, 4, 5 grow out, tbo youngest onos thoroforo always 

 ttiriiing towards tbe leaf b. The i n t • inode next above tbo si-alo mm-li elougated (»' of tbe braneh 1 and so on). The two intei- 

 nodoa of eacb bran. -b beneath it, on tho contrary, extremely abbreviated, all taken togetber forming a sympodium of only a few 

 mm in Icngth ( 1 1 1 1 1 • - 1 1 Bhorter, thus, than in tbe tigun) incliidod within the basal part of tho sheath. /•-', Hibernating tnrio, nat. 

 Bize; explanation, seo the texi and the explanation of the tnrio of /'. flliformis Pxrb., p. is. 



Uppsal.), and Malö Briochovskij island, 1876, Sahlberg (hb. Stockh.). The latter 

 island ia situated on 70° 50' N. L., and P. subretusus therefore seems to be the most 

 northern Potamogon-spccies of the world (see under the following!). 



I*, Yii&iiiatiis Turczaninow. 



Flora Bakalensi-Dahurica, — in Hull. Soc. Imp. des naturalistes de Moscou 

 1 854, T. XXVI 1 . 2 (1 partie, p. 66. - Cfr Kihlman, Pol. vaginatua Turcz., ny för 

 Europas Flora, in Meddelanden af Soo. Fauna et Fl. fenn. 14. 1888, 111 — 115. — 

 Fig. 11 and 12. 



