. Critical researches on the potamogetons. KUNGL. SV. VET. AKADEMIBNS HANDUNGAE. BAND 55. N:0 5. 83 nervation of leaves and ligules. It joins to the Polygoni {Ochreati and Compressi) by the leaf-base also, but differs by the structure of the peduncle, stem, and leaves. The two species here below considered have the front-field of thestipularsheathslO—15-fibrous, in this respect also keeping a me-^ dium position between the two groups mentioned above. If the Oxyphylli nevertheless be con- sidered, on accountof thestylesand stigmas, to belong to the Pusilli, they must, however, form a sepa- rate
. Critical researches on the potamogetons. KUNGL. SV. VET. AKADEMIBNS HANDUNGAE. BAND 55. N:0 5. 83 nervation of leaves and ligules. It joins to the Polygoni {Ochreati and Compressi) by the leaf-base also, but differs by the structure of the peduncle, stem, and leaves. The two species here below considered have the front-field of thestipularsheathslO—15-fibrous, in this respect also keeping a me-^ dium position between the two groups mentioned above. If the Oxyphylli nevertheless be con- sidered, on accountof thestylesand stigmas, to belong to the Pusilli, they must, however, form a sepa- rate series within this subsection. Their nearest relative among the Pusilli may be P. orientalis Hagstr. Assumably P. sibiricus Ar. Benn., p. manchuriensis Ar. Benn. and P. Henningii Ar. Benn. are to be included with the oxy- phyllus-group, and the distribution area of the group would thus be decidedly Asiatic. P. oxypliyllus Miquel. Annales Mus. Bot. Lugduni-Batav. Ill, 1867, 161. — Fig. 32. Stem and peduncle compressed so that the crosscut-form becomes oval (2—3 : 1), the former sometimes sligtly canaliculate, both of about the same thickness. The anatomy is the one common to the body of the small-leaved species, but the epidermis-cells are comparatively broad, about 2—3 times as long as broad. The subepidermal bast-bundles are strong, but no pseudo-hypoderma has been observed. For the rest I refer to the fig. 32, D. The central axis. Fig. 32. P. oj-i/pJii/Jhis MiQ. A, a, basis and b top of a stem-leaf, Y. B, Pistil, o, lateral view, b, from above, c, ventral view, y ; ^> Transverse section of a stem-leaf, showing the lacunar system (I), vascular bundles [m, n'), and the mechanical strands (str), lower half, ^y**; Z>, Transverse sec- tion of stem, cc, central axis, str, subepidermal strands, ^» ^> Transv. sect, of the peduncle, showing the lacunte (/) and vascular bundles (hatched), V- shows the usual oblong diagram. The two median vascular bundles run close to
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