. Critical researches on the potamogetons. KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BANn 55. N:0 5. 153 The epidermis, otherwise in general consisting of elongated cells, about 5 times as long as broad, consists here of very short cells of more or less regular cubic form. Inside the epidermis settle 2—4 layers of parenchymatous cells of the same form as the common cortical cells, but to the size generally a little smaller than those. The bottom of the lacuna is extended across those cells (Fig. 69, B, a). In species with 2- or more-celled pseudo-hypoderma no increase takes place and, there- fore
. Critical researches on the potamogetons. KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BANn 55. N:0 5. 153 The epidermis, otherwise in general consisting of elongated cells, about 5 times as long as broad, consists here of very short cells of more or less regular cubic form. Inside the epidermis settle 2—4 layers of parenchymatous cells of the same form as the common cortical cells, but to the size generally a little smaller than those. The bottom of the lacuna is extended across those cells (Fig. 69, B, a). In species with 2- or more-celled pseudo-hypoderma no increase takes place and, there- fore, no external protuberances are to be found. P. pulcher has only a single cell- stratum and, accordingly, papillae are formed. As the figure above shows P. pulcher has only a single strengthening stratum and lacks subepidermal strands. Interlacunar strands occur neither in the stem nor in the petioles. The central stele of the stem is surrounded by an 0-endodermis. Vascular bundles arranged according to the diagram in fig. 80 with four median bundles, that is to say a bundle-trio and an opposite bundle. The species can easilj' be recognized by its narrowly ovate-lanceolate, short- petioled, submersed leaves with broad lacunar part along the midrib as far as the very apex and feeble ligules. The pistils are those typical to the group. Pollen small-grained. The species occurs also without true submersed leaves: f. aiiiphibius n. f. — Fol. omnibus coriaceis vel subcoriaceis. Distribution: U. S. of N. America: Delaware, 74, Canby (hb. Uppsal.), Nov. Angl., TucKERMAN (hb. Uppsal.), Massachusetts, several stations: Ashland, Naticks, Readvill, 80—82—83, Morong (hb. Stockholm.), f. amphibius; Apponang Pond, Rhode Island (hb. Stockholm.). P. rotiiiidatus n. sp. — Fig. 70. Caulis subhumilis (± 30 cm) teres simplex, internodiis 2—5 cm longis, a foliis floralibus ramis l:se—2:ae ordinis prolongatus. Folia submersa subcoriacea, infimum phyllodio simile, cetera longe petiolata
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1910, bookyear1916
