. Critical researches on the potamogetons. KUNGL. SV. VET. AKADBMIBNS HANDLINGAE. BAND 55. N:0 5. 251 in distinction to tlie Natantes and the Luceiites, the stone-cells of which are very thick-walled and hard. â Leaf-apex of P. prcel. always cucullate and the margin smooth. Anatomically P. prcelongtis belongs to the species which are rich in scleren- chyma, while P. perfoliatus, again, is a non-sclerenchymatous form and even lacks the interlacunar ligular bundles in the stem-cortex. The former has consequently very numerous bast-bundles in the stem as well as in the peduncle, in the midrib of
. Critical researches on the potamogetons. KUNGL. SV. VET. AKADBMIBNS HANDLINGAE. BAND 55. N:0 5. 251 in distinction to tlie Natantes and the Luceiites, the stone-cells of which are very thick-walled and hard. â Leaf-apex of P. prcel. always cucullate and the margin smooth. Anatomically P. prcelongtis belongs to the species which are rich in scleren- chyma, while P. perfoliatus, again, is a non-sclerenchymatous form and even lacks the interlacunar ligular bundles in the stem-cortex. The former has consequently very numerous bast-bundles in the stem as well as in the peduncle, in the midrib of the leaf and in the ligules, to which may be added that P. prcelongus has also a well developed ^t-endodermis in the stem, whereas P. perfoliatus has o-endoder- mis. Judging from these and other facts P. perfoliatus seems to represent a more primitive type than P. prcelongus. It approaches also obviously to P. densus. It may be remarked that among all known species P. prce- longus has the longest peduncles, as much as 65 cm long. From the fossil occurrence of the two species in Scanian peat- mosses it is clear that P. perfoliatus has immigrated to Sweden almost immediately after the melting of the land-ice and that P. prcelongus. A, Lowest stem-leaf, -J, showing Fig. 116. AâF, Pi-telongus Wulf. the form of the base of the 1â4 lowest leaves. i>, Pistil, side-view, ^'{ â C, Transverse section of the fruit, '{-, I, lid, p, putaraen, f, epicarp. has followed rather close upon its â '^' P="' °f â¢â ' transverse section of the stem, \», showing the position of the pseudo-hj'podermal strands, str, ep, epidermis, 7ip, the two-layered pseudo-hypoderma, il, intercellular lacuna, vb, vascnlar bundle of the ligular circle, inside which there are 3â4 circles of bundles, iv, inter- lacunar wall. E, Surface section of the epidermis, \^. F, Transverse section of the lacunar portion of a fullgrown stem-leaf {lower half), \°, m, mid-bundle, vb, vase, bundle, sty, bast-b
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1910, bookyear1916
