218 



J. O. HAGSTROM, CR1TICAL RESEARCHES ON THE POTAMOGETONS. 



Witli t lie same right as for instance the name of P. nitens Weber is used of all 

 the forms of the hybrid P. gramineus X perfoliatus, the name of P. sparganifolius of 

 Ljestadius ought also to be applied to the hybrid here concerned, as the description 

 as well as all specimens delivered by Ljestadius must be referred to it. Cfr 

 also S. Almquist, on P. sparganifolius in Bot. Not., 1891, 129! The Richterian 

 name is certainly attributed to the hybrid granlin. X natans as its particular name, 



but this, I think, can nowise dis- 

 place the right of priority being 

 due to the Laistadian name. 



As mainform, f. typicus. 1 

 therefore regard the Lapland form 

 and the crosses from North Europé 

 congruent to it, usually with elong- 

 ated stem, of ten extremely long 

 and very narrow submersed teaves, 

 and nearly alwaya narrowly lan- 

 eeolate or long-lanceolate f loating 

 leaves. 



The other crosses are by 

 Ascherson and Graebner di- 

 stributed on the varr. pcrgrami- 

 neus: »untergetauchte Blätter sehr 

 läng und schmal linealisch» and 

 pernatans: those leaves »kurser und 

 breiter, lanz. — längl. lanz.» It 

 would thus be the var. pergranii- 

 neus which resembles P. natans, 

 and the v. pernatans which is like 

 P. gramineus. Cfr S. Almquist 

 in Hartman, Skand. Fl., ed. 12, 

 1889, 48! To those KuPFFEB 

 adds a f. inlennedius, which in 

 habit is said to stånd about half- 

 way between the two parents: 

 »halt im Ausseheii ziemlich gul 

 die Mitte zwisehen den Eltern . 

 In all its forms P. sparganifolius is best distinguiehed from P. Juans \ natans 

 by its upper leaves, being less eonspicuously and not so sharplv CUSpidate and, be- 

 ^i(le.s ) longer Btalked (petioles usually longer bhan the låminse). Cf. the tigs. 104 and 



121! The form typicus has the base of those snheoriaceons leaves usually sloping; 

 Ihc morfi soutli forms are usually inorc lichly endowed with floating leaves, which 

 have rounded or BUbcordate base and the apex short, obtusely mucronate. 



Fig. U)4. I', sparganifolitu Lsst. A — /•', Different forma of the bladea 

 ■ .i th< folia floralia, ] . /•', Oross-sectlon of a Bubmersed leaf Bhowing the 

 arrangemenl of ui rvea, Babepidermal atranda and lacnns, V, belouging to 

 iii' .M lati i imlt plant, si • belon I 



