KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. NIO 5. 241 



holm., Lund., Brem.); »E loco Nolteano, Sönder (hb. Uppsal.); > Holstein und Lauen- 

 burg», E. F. Nolte» (hb. Stockholm., Uppsal.); Ejdern at Rendsburg, 44, Nolte 

 (hb. Uppsal.); Holstein, Poulsen (hb. Uppsal.). It is these German specimens G. 

 Fischer names f. perlucens or sublucens of a »series genuinus». Marchia prope Bero- 

 linum, 88, (hb. Stockholm.). — Austria, Austria superior prope Hallstatt, Stapf (hb. 

 Lund.). — England, Surrey, Wey & Arun Canal, 88, Beeby (hb. Stockholm., Upp- 

 sal.); Cambridgeshire, The Engine Drain, Mepal, 90, Fryer (hb. Stockholm., Upp- 

 sal.); A. Fryer has labelled it: »P. crassifolius mihi = coriaceus X natans ? » and not- 

 ed: »This plant differs from P. flintans Roth by the submerged leaves at the 

 time of flowering being distinct stalked like the upper f loating leaves and by the 

 petiole being flat above, not convex as in fluitans». But those properties do not 

 point especially to P. gr -aminens in contradistinction to other -»fluitans^ (= lucens X 

 natans); Of course the plant might be Zizii X natans, but I think it impossible to 

 demonstrate it. Horselode Fen Drain, by the 16 acre Gate, Chatteris, 90, Fryer 

 (hb. Stockholm.), lab. >P. crassifolius mihi var. = Zizii X natans. petiolatus Wolf- 

 gang?» 



A plant from Russia, Guv. Minsk, 93, Paczoski (hb. Petersb.) might also be 

 this hybrid. It differs by the dark green colour and by the upper leaves being non- 

 coriaceous. The colour reminds much of P. prcelongus. No other stations are known 

 to me. 



P. luceilS L. X nodosus Poir. (P. subrufus n. hybr.). 



Caulis ssepe altus robustus simplex. Folia submersa omnia ± longe petiolata 

 lanceolata ± acuta vel ± obtusa, ± serrulata; suprema ± coriacea, petiolis lamina 

 brevioribus, saepe rufescentia obtusa. Ligulce tenues longa? olivaceae ± conspicue bi- 

 costatse. Pollen sterile. 



In the Museums here this hybrid is present in specimens from two far sepa- 

 rate stations, one European and one North-American. They are characterized by 

 the high-grown, of ten stout, unbranched stem, usually prolonged by a branch from 

 the base of the primary spike. Topmost leaves more or less coriaceous, lanceolate 

 with shorter petioles than the blades, obtuse, often red-brown, 15 — 20x2,5 — 3 cm; 

 lower leaves petioled, lanceolate, finely serrulate, apex now like P. nodosus, now more 

 like that of P. lucens, which is also the case with the nervation and the consistency, 

 always more durable than in P. nodosus, and with more persistent ligules, being thin, 

 long, brown, and more or less bicarinate. Spikes and peduncles as in the parent- 

 species. Pollen sterile. Stem-anatomy intermediate: 1) Subepidermal strands mostly 

 wanting, 2) interlacunar bundles in 1 — 3 circles, always fewer than in P. lucens, 3) 

 endodermis of weaker, one-sidedly thickened cells than has P. lucens. Beside the leaf- 

 serrulation these three facts thoroughly contradict a supposed combination of lucens 

 X natans. 4) The vascular bundles of the stele are arranged now as in P. lucens, 



K. Sv. Vet. Akad. Handl. Band 55. N:o 5. 31 



