218 



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



With the same right as for instance the name of P. nitens Weber is used of all 

 the forms of the hybrid P. gramineiis X ■perfoliatus, the name of P. sparganifolius of 

 L^STADius ought also to be applied to the hybrid here concerned, as the description 

 as well as all specimens delivered by L^stauius 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 gramin. X nutans as its particular name, 



but this, I think, can nowise dis- 

 place the right of priority being 

 due to the Lsestadian name. 



As mainform, f. typicus, I 

 therefore regard the Lapland form 

 and the crosses from North Europe 

 congruent to it, usually with elong- 

 ated stem, often extremely long 

 and very narrow submersed leaves, 

 and nearly always narrowly lan- 

 ceolate or long-lanceolate floating 

 leaves. 



The other crosses are by 

 AscHERSON and Graebner di- 

 stributed on the varr. pergrami- 

 neus: »untergetauchte Blatter sehr 

 lang und schmal linealisch» and 

 pernatans: those leaves »kiirzer und 

 breiter, lanz. — langl. lanz.» It 

 would thus be the var. pergranii- 

 neus which resembles P. nutans, 

 and the v. pernatans Avhich is like 

 P. gramineiis. Cfr S. Almquist 

 in Hartman, Skand. FL, ed. 12, 

 1889, 48! To those Kupfeer 

 adds a f. intermed'kis, which in 

 habit is said to stand about half- 

 way between the two parents: 

 »halt im Aussehen ziemlich gut 

 die Mitte zwischen den Eltern». 

 In all its forms P. sparganifolius is best distinguished from P. lucens x natans 

 by its upper leaves, being less conspicuously and not so sharply cuspidate and, be- 

 sides, longer stalked (petioles usually longer than the laminae). Cf. the figs. 104 and 

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

 the more south forms are usually more richly endowed with floating leaves, which 

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



Fig. 104. P. sparganifolius L.est. A — E^ Different forms of the blades 

 of the folia fioraiia, ]-. F\ Cross-section of a submersed leaf showing the 

 arrangement of nerves, subepidermal strands and lacuna^ '^f, belonging to 

 the Misterhnlt plant, see below ! 



