. Critical researches on the potamogetons. 82 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE Fig. 31 A—C, P. polygonus Ch. & Schl. A, Transverse section of leaf below the middle, \f^, showing the lacnnar system (/) and the bast-bnndles; str^ marginal strand; ?/(, «', nerves (vascular bundles); B, Pistil; a, lateral view, h, ventral view, ^^', C, Trans- verse section of the central axis of the stem, showing the bundles and their channels, ^0. ^ D—F, P, Ulei ScHuar. D, Transverse section of stem, showing the arrangement of the lacunar system, the subepidermal strands {str\ and the
. Critical researches on the potamogetons. 82 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE Fig. 31 A—C, P. polygonus Ch. & Schl. A, Transverse section of leaf below the middle, \f^, showing the lacnnar system (/) and the bast-bnndles; str^ marginal strand; ?/(, «', nerves (vascular bundles); B, Pistil; a, lateral view, h, ventral view, ^^', C, Trans- verse section of the central axis of the stem, showing the bundles and their channels, ^0. ^ D—F, P, Ulei ScHuar. D, Transverse section of stem, showing the arrangement of the lacunar system, the subepidermal strands {str\ and the vascular bundles of the central cylinder {cc)^ X occasionally occurring interlacunar bundle, 'Y > ^. Top of a stem-leaf, ^; F, Transverse section of this leaf, at the middle, vi, n', sir, as in are either quite wanting or present in a very slight number. The crosscut-form of the central stele is rhomboid, which results from the median bundles running more separately than in general and the latera,! ones being considerably reduced both in number and size, the stele thus presenting a four- bundled diagram. The leaves taper more abruptly into an apex, less acute by far than in P. polygonus. The leaf is through its whole width and up to the very top intersected or replenished with harrow channels, the crosswalls of which are rather approximate, which makes it appear reticulate under the lens. Two vascular bundles run on either side of the main-rib and, between them, thin bast-bundles nearly as in the foregoing species, but the border-strand is considerably weaker. Ligules more durable, their front-field is 12—15 (17)-fibrous. It should be observed, that my researches are made on young shoots from a creeping rhizome, the only materials hitherto accessible to me. Spike-bearing indivi- duals may have the interlacunar sclerenchyma (the ligu- lar bundles) a little more developed. The species is figured in Graebner, Potamog. ap. Engler, Pflanzenreich IV, 11, 1907, 105, f. 25 A
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1910, bookyear1916
