. Critical researches on the potamogetons. 14'6 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. grammeus var. graminifolius Fk. by S. Almqtjist in Bot. Not., 1889, 66, are not this hybrid, see under P. gramineus L. — Norivay, Senjen, Bryggehaug, 10, Noto. P. nericius must until further be looked upon as a most rare plant. P. alpimiS Bale. X natailS L. (P. Driicei Fryer, Potamog. of the British Isles, 1898, 31, t. 21). — Fig. 66. There can scarcely be any doubt of the hybrid nature of the Berkshire plant named P. Drucei (Fryer 1899, as a full species). The large floating leaves di- sti
. Critical researches on the potamogetons. 14'6 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. grammeus var. graminifolius Fk. by S. Almqtjist in Bot. Not., 1889, 66, are not this hybrid, see under P. gramineus L. — Norivay, Senjen, Bryggehaug, 10, Noto. P. nericius must until further be looked upon as a most rare plant. P. alpimiS Bale. X natailS L. (P. Driicei Fryer, Potamog. of the British Isles, 1898, 31, t. 21). — Fig. 66. There can scarcely be any doubt of the hybrid nature of the Berkshire plant named P. Drucei (Fryer 1899, as a full species). The large floating leaves di- stinctly indicate that P. nutans is to be considered as one of the originators. A closer investigation of all the organs of the plant does not contradict the sup- position either. But which the other parent species may be is not quite a matter of course. The first proposition of Druce on P. alpinus, however, seems to be favoured with all probabihties. The long petioles of the floating leaves certainly seem to be adverse to it, but they are likely to originate from local condi- tions (River Loddon). The leaf-base is sloping as in P. alpinus and in the river-form of P. naians which also has long petioles. The floating leaves besides appear very early, already below the primary spike, which confirms the supposition that either of the two parent- species is furnished with coriaceous leaves. The sub- mersed leaves are also long-stalked as the other natans- hybrids. The ligule can be said to be intermediate, 75—85 mm long (P. nat.), brown (P. alp.) with faint ridges. The styles and stigmas remind of P. polygoni- folius almost more than of nutans, but the smallness of the stigma, especially, may depend on deformity, a usual occurrence in the hybrids. We are so much the more inclined to think so, having seen specimens culti- vated in the Botanical Garden of Copenhagen with al- pmMs-stigmas. A cross-section of a spike-bearing stem shows a structure very obviously confirming the presu
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