. Critical researches on the potamogetons. KtTNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 145 P. alpinus Bale, x graiiiiiieus L. (P. nericiiis Hagstr.). — Fig. 65. The few specimens of this hybrid hitherto found can be described as follows: Caulis teres subcrassus (ut in P. alpmo) simplex vel (ad medium) ramulo debilissimo (interm.) instructus. Folia sub- mersa lanceolata, superiora + petiolata laminis decurrentibus apice ± obtusa, ramulina apice siibcuspidata ± obtusa, omnia integerrima; natantia lanceolata obtuse cuspidata, petiolata et laminis decurrentibus ut in P. alpino. Ligulae
. Critical researches on the potamogetons. KtTNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 145 P. alpinus Bale, x graiiiiiieus L. (P. nericiiis Hagstr.). — Fig. 65. The few specimens of this hybrid hitherto found can be described as follows: Caulis teres subcrassus (ut in P. alpmo) simplex vel (ad medium) ramulo debilissimo (interm.) instructus. Folia sub- mersa lanceolata, superiora + petiolata laminis decurrentibus apice ± obtusa, ramulina apice siibcuspidata ± obtusa, omnia integerrima; natantia lanceolata obtuse cuspidata, petiolata et laminis decurrentibus ut in P. alpino. Ligulae intermedise, debiliores quam in P. gramineo, subbicarinatse, fuscovirides. Pedunculus vix incrassatus. Spica sterilis. The colour of this plant reminds of P. gramineus more than of alpinus, but in habit it resembles most the latter, although the stem, at the middle, usually has a short and very faint branch (influence from P. gramineus). Very signi- ficant are the dark-green submersed leaves the structure, nervation, and smooth margins of which are most like those of P. alpinus. Their tops taper gradually or end with a slight cusp and are always a little more obtuse than in P. grami- neus (influence from P. alpinus). The floating leaves resemble as to stalk, and the size and form of the blade, nearest P. alpinus, but the apex is intermediate with a very faint and obtuse cusp. All the ligules are paler than in P. alpinus, which they otherwise resemble as to structure, the basal nerves being by far fainter and the keels lower than in P. gramineus. The styles are not in such a state that they can be examined. The anatomy of the stem: Cortical strands as in P. gramineus, sometimes, however, a little weakened. The arrange- ment of the vascular bundles of the central cjdinder varies, in the common way of the hybrids, from more alpinus-\i\ie to almost quite gramineus-s\\a.\}%A. Endodermis of one-sidedlj' thickened it-cells as has P. gramineus, but influenced by P. The medmn bundl
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Keywords: ., bookcentury1900, bookcollectionbiod, bookdecade1910, bookyear1916
