. Critical researches on the potamogetons. .44 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. farther to the north, for instance at Nikandrowsky ostrov, 70° 20' n. L. (coll. Lund- STROM, 75, Arnell, 76, hb. Stockholm.). From this boundary it spreads southwards through all parts of the world, its distribution consequently being universal and sur- passing all the other species of the genus. It is evident that a species, appearing under so different climatic conditions, arctically (see above!) and equatorially (for instance in the Albert Edward Lake, Africa, coll. R. E. Fries, 1912, ^ ~
. Critical researches on the potamogetons. .44 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. farther to the north, for instance at Nikandrowsky ostrov, 70° 20' n. L. (coll. Lund- STROM, 75, Arnell, 76, hb. Stockholm.). From this boundary it spreads southwards through all parts of the world, its distribution consequently being universal and sur- passing all the other species of the genus. It is evident that a species, appearing under so different climatic conditions, arctically (see above!) and equatorially (for instance in the Albert Edward Lake, Africa, coll. R. E. Fries, 1912, ^ ~ ^ —^ hb. Upps.), and occurring both in salt and fresh water, at the shores of the sea and in small lakes, in rivers and rivulets, on muddy, fat ground and bar- ren, sandy, clay bottom, must, of course, be met with in many different varieties or forms. Thus we find forms with horse- hair-like stems and leaves and, again, stems 2 mm in diame- ter at the base and with 5 mm broad stem-leaves and number- less transition forms between those extremities; with short and long sheaths (at most 50 mm); wdth large (4,5 x 3 mm) and smaller (3x2 mm) fruits (megacarp and microcarp forms). Of all the variations of this species I have observed, none seems to be more significant or of a greater systematic value than the different forms of the leaf-apex, of which the figure beside should give an idea. The body of the forms should be divided into the two varieties established here below, according as their leaf-apex is endowed with a conspicuous mucro or more slowly tapered. The somewhat peculiar v. mongolicus A. Benn. ought to be kept, and likewise the P. zosteraceus Fries and P. striatus R. & P. All the other innumerable varia- tions should after my opinion be considered only as rather accidental and insignifi- cant forms of inferior value. The following arrangement of the forms of P. pedinatus is only an attempt to put in order the great multitude of forms which I have had an opportunit
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1910, bookyear1916
