. Critical researches on the potamogetons. KUNGL. SV. VET. AKADEMIENS HANDLTNGAE. BAND 55. N:0 5. 179 belg. 1827, 163. — P. Hornemanni Meyer, ex Koch, Synopsis, 1837, 674. — P. microcarpus Boiss. & Reut., Diagn. PL nov. Hisp, 1842, 24? — P. siculus Tineo ap. GussoNE, Fl. Sic. Syn., II, 1845, 790. — P. subflavus Lobet & Barrandon, Flore de Montpellier, 1876, 671. The floating leaves of this species are generally thinner than in other species dependent on a reduction of the palisade-tissue into one or 2 cell-strata of cubic cells without the air-rooms appearing there otherwise. Rarely we
. Critical researches on the potamogetons. KUNGL. SV. VET. AKADEMIENS HANDLTNGAE. BAND 55. N:0 5. 179 belg. 1827, 163. — P. Hornemanni Meyer, ex Koch, Synopsis, 1837, 674. — P. microcarpus Boiss. & Reut., Diagn. PL nov. Hisp, 1842, 24? — P. siculus Tineo ap. GussoNE, Fl. Sic. Syn., II, 1845, 790. — P. subflavus Lobet & Barrandon, Flore de Montpellier, 1876, 671. The floating leaves of this species are generally thinner than in other species dependent on a reduction of the palisade-tissue into one or 2 cell-strata of cubic cells without the air-rooms appearing there otherwise. Rarely we meet with leaves with air-cells in that tissue, which then is very like ordinary palisade tissue. Apex of the floating leaves usually obtuse without distinct cuspidation or pointing (see fig. 93, B). Exceptionally there are individuals with the upper leaves cuspidate. I name this form: f. cuspi( n. f. — Folia superiora cuspidata (vide fig. 93, A). Sometimes the floating leaves are small, 20—30 X 10—15 mm, and the submersed leaves narrow: f. subflavus n. f. — P. suhjlavus Lor. & Barr., 1. c. — Spe- cimens from France, Mauguio (Herault) 73, Loret and others (hb. Stockholm, et Lund.) and from Germany, Daunstadt (Palati- nat) 55, Schultz (hb. Stockholm, et Uppsal.). This plant is still held for a subspecies of P. alpinus Bale. by Prof. P. Graebner in his Synopsis der Mitt. Fl. 1912 p. 476 (2d ed. Ill Lief.). Prof. G. Fischer writes (in Fedde, Repert. 1914) of the same plant: — »certe et habitu et fructu distat a P. alfinus Bale, et accedit ad P. coloratum. Utrum autem subspe- cies vel proles P. colorati, an planta hybrida inter P. coloratum et P. alpinum (vix P. polygonifolium) habendus sit, adhuc am- bigiturs. The Heraultian plant is without any doubt a true form of P. coloratus and not at all of a hybrid origin. — A form with rounded, ovate, superior leaves, ca. 30 X 24 mm, is V. rotundifolius Mert. & Koch. — Now and then forms appear with
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