KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 215 



A specimen of f. communis Hagstr. in herb. Nat. Hist. Mus. Stockh. is evidently 

 mislabelled »Piteå Lpmk» (see also S. Almquist, 1. c!) without closer statement of 

 locality or collector. Without doubt it originates from Mjösjö, Jemtland, vvhere the 

 same form is gathered by Tiselius (1881) and others. — A great many specimens 

 are preserved in the Museums of Stockholm, Uppsala and Lund. 



Denmark several stations, especially in the islands (hb. Stockholm., Uppsal., 

 Lund., Gothenb.). — Norway, Asker, in Semsvand Növik (hb. Stockholm.), f. longi- 

 pedunculatus, Gjellumvand etc; Jarlsberg in Fossanelven, Hadeland, Frosta and Rome- 

 rike (hb. Christiania). — England, Cauldshiels Loch, Melrose Roxburgh, 79, Brotherston 

 (hb. Lund.); Coniston Lake, N. Lancashire, 82, Baily (hb. Stockholm.), f. foliosus (Tis.) 

 Hagstr.; Cambridgeshire: Doddington, Sutton, Chatteris, and Mepal, scattered, gather- 

 ed by Fryer (hb. Stockholm, et Uppsal.) mostly developed according to the validus- 

 type and vvith floating leaves, f . coriaceus (P. coriaceus Fryer) ; but the other forms 

 are also represented in typical specimens and transitions between them; Hunting- 

 donshire, likewise in several places, coll. Fryer (hb. Stockholm.) among others a 

 rare cornutus-iorm (no. 1188), see fig. 103, B! - - N. Wales, Llwidiard Lake, 84, 

 Griffith (hb. Stockholm.). — Scotland, Kingham Loch, 74, Dr Boswell Syme; 

 »lucens with floating leaves» ex Syme; conspicuous P. Zizii. — Ireland according 

 to A. Bennett in Journ. of Bot. 1881, 312. — Finland, Savonia borealis, par. Jor- 

 vis in lacu Valvatos, 93, Lindberg; Åland, Hammarland in a lake, 09, B. Flor- 

 ström (hb. C. G. Alm). — Germany, Pommern, Gutsdorf, 81, Sydow (hb. Gothenb.), 

 f. communis Hagstr.; Wittbeck b. Ratzeburg, Nolte (hb. Stockholm.), f. coriaceus 

 M. K., Kiliae, Nolte (hb. Stockholm., Uppsal.), f. communis Hagstr., labelled: »P. 

 lucens — angustijolius-»; Siisil, Hols., hb. Engler (hb. Berolin.) lab. »natans X gramineus 

 od. vielleicht gram. mit polygonifolius» »P. Graebner det.»; Sileciae (hb. Uppsal.), f. 

 communis Hagstr.; Dresden, Hubner (hb. Stockholm.) elongatus-i orm; »Egelse Saxon. >, 

 45, Hubner (hb. Stockholm.), f. communis Hagstr.; Berlin, Grunewald See, 86, 

 Scheppig (hb. Stockholm., Uppsal, et Berolin.), validus-form, labelled. »P. decipiens 

 Nolte», låter on by P. Graebner named P. berolinensis, and lastly regarded as a 

 variety of P. lucens X prcelongus (Potamog. 1907, 137) or as a P. lucens X gramineus 

 but not a P. Zizii-form (Synopsis 1913), corresponds nearly with f. lucescens with 

 rather broad (20 — 25 mm) short-petioled leaves and intermediate ligules, has nothing 

 to do with P. prcelongus Wulfen. Bavaria bor., Erlangen, 89, Gluck and others 

 (hb. Stockholm., Uppsal.) f. communis Hagstr. — France, Lac d'Annecy (Savoi), 

 Didier (hb. Stockholm.), elongatus-iovm ; Vauville (Manche), Corbiére (hb. Stock- 

 holm., Lund.), f. communis Hagstr. — Switzerland, Zurich, 81, Jäggi (hb. Stock- 

 holm.). — Italy. A plant in the Nat. Hist. Museum (Bot.) of Stockholm, accord- 

 ing to the label (»Herb. sic. ») originating from Sicily, belongs also to this hybrid. 

 This station is the most south of Europé. As P. gramineus L., as far as I know, 

 is not at present met with in Sicily, this Zizii-iorm may be a remainder from 

 past times. But of course it is also possible that, from a more northern locality, it 

 has any way been brought to its present place. It is in all parts a P. gramineus x 

 lucens f. communis Hagstr., but is by Tineo held for a lucens-iorm and also by 



