. Critical researches on the potamogetons. KTINGL. SV. VET. AKADEMIENS HANDLINGAE. BAND 55. N:0 5. 115 bundles. Inside this stratum there is a circle of large-roomed lacunse. Central stele compressed and its bundles arranged according to the oblong stele diagram in three groups with three xylem portions. The stem-leaves are provided with sclerenchjanatous strands in the lacunar part but the marginal strand is thin and there is no tendency to form bast-bundles like those characteristic to the Compressi. The leaves are 3—5-nerved and not at all digressing from the pusilIus-tyY>e as to the ner
. Critical researches on the potamogetons. KTINGL. SV. VET. AKADEMIENS HANDLINGAE. BAND 55. N:0 5. 115 bundles. Inside this stratum there is a circle of large-roomed lacunse. Central stele compressed and its bundles arranged according to the oblong stele diagram in three groups with three xylem portions. The stem-leaves are provided with sclerenchjanatous strands in the lacunar part but the marginal strand is thin and there is no tendency to form bast-bundles like those characteristic to the Compressi. The leaves are 3—5-nerved and not at all digressing from the pusilIus-tyY>e as to the nervation. i>The closely packed veins» are the side-walls of the lacuna3 and »the cross veins» are their cross-walls. The lacunse do not occupy the whole space between the midrib and the lateral nerves in the upper half of the leaf. (See the figure!) A plant labelled sRaikie's Niger Expedition 1857—59. Nupe. Coll. C. Barteri (lib. Stockholm.) lacking floating leaves in the spike-region and resembling P. Preussii as well as P. java- nicus might be of a hybrid origin. The stigmas are very small, - by far not covering the upper surface of the style. Leaves as in P. javanicus. Ligules few-nerved in the front-field. Pollen small-grained, well-shaped. No fruit seen. Subseries b. Obtusi Hagstr. The boundary-line between these two subseries is not very marked. Some forms of P. pusillus have obviously tapering leaves and the leaves of P. obtusifolius have a lacunar system with subepidermal strands (see the figs.) and I have said above that the P. Asch. f. pusiUoides m. has pretty soft and flexible leaves; however, this arrangement can ad interim serve the purpose to give a survey of the species belonging hereto, until better know- ledge is obtained as to the pistils and fruits. ° ^ Fig. 50. P. JPiviissii Bens. A, Top of .1 , ',»• B, Transverse section of a stem-leaf at the middle, /«, midvein, n\ n^, lateral veins. sir, scler. strands, ^. C, Transverse section of s
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1910, bookyear1916
