KUNGL. SV. VET. AKADEMTENS HANDLINGAR. BAND 55. NIO 5. 231 



stadt, 55, Brockmuller (hb. Stockholm., Uppsal.), f. typicus; Silesia, 89, Hellwig 

 (hb. Stockholm.), North Germany, B^enitz (hb. Gothenb.), f. robuslior. — England, 

 Surrey, 88, Beeby and others (hb. Uppsal.), f. typicus; Cambridgeshire, Witcham 

 Meadlands, Mepal, 87, Fryer no. 492 (hb. Stockholm.); Huntingdonshire, Stocking 

 Fen, Ramsay, 89, Fryer, no. 1265 (hb. Stockholm.), f. typicus, lab. »Potamogeton 

 jalcatus Fryer», Fryer scrips; Canal Aldershot, S. of Engl., 81, Bennett (hb. 

 Stockholm.), labelled »P. heterophyllus Schreb. var. pseudo-nitens mihi. J. of Botany 

 1881 p. 344», Benn. scrips., consequently an authentic specimen, but without spi- 

 kes, an unambiguous P. nitens with half-clasping leaves. — Scolland, White Loch, 

 E. Pertshire, 82, Sturrock (hb. Stockholm.) lab. »P. heterophyllus var. pseudo-ni- 

 tens mihi» Benn. scrips., lacking spikes but a clear P. nitens; Kirbiston Loch, Ork- 

 ney Isles, J. B. Syme, 75 (hb. Stockholm.). — Russia, Petersburg, ins. Krestofsky, 

 Regel (hb. Stockholm.), f. obtusus, a dubious form, peduncles and topmost branch- 

 leaves reminding of P. gramineus ; possibty, however, a genuine P. perfoliaius; »Gu- 

 bern. Perm» (hb. Brem.); Petrosavodsk (hb. Brem.). — Finland, Alandia, Geta, 01, 

 Palmgren and Klingstedt (hb. Stockholm.). — 



N. America, Milwaukee, Wisconsin, Lapham (hb. Uppsal.), f. restrictus; Put- 

 nam, Conn., 71, J. W. Robbins (hb. Hagström). — P. nitens seems to be a rare 

 plant in N. America, which should be looked for. Robinson and Fernald do not 

 mention it in Gray's New Manual, of 1908. 



P. gramineus L. x polygoiiifolius Pourr. 



(P. Seemenii Asch. et Graebner, Synopsis mitteleur. FL, I, 1897, 335). 



A true form of this hybrid lies under no. 139 in Tiselius, Potam. suec. exsicc. 

 (hb. Stockholm., Uppsal., Lund., Gothenb.) named P. gramineus f. lanceolatijolius Tis. 

 Tiselius is of the view that the deviating peculiarities of this plant originate from 

 »naturå loci et modo vivendi». It proves, however, to possess all the characteristics 

 of a hybrid plant. The pollen is sterile, and in every part of the plant two special 

 principles are contending about the dominancy över the form. 



a lanceolatifolius (Tis.) Hagstr. — Folia submersa inferiora sessilia vel breviter 

 petiolata laminis anguste decurrentibus, apice attenuata vix subcuspidata, superiora 

 ± petiolata, summa coriacea basi lanceolata. Ligulce caducse, 2 — 3 cm longae; spica 

 parva, 9—11 (17) mm. 



The submersed leaves are very characteristic. Their base lanceolate with a 

 short stalk, or with the lamina narrowly decurrent as far as the insertion, often with 

 a conspicuous waist-like contraction between the stalk-like part and the blade (see 

 the fig. 109, ^4); margin often unteethed, but sometimes (from the same locality) a 

 very faint rudimental serrulation, at greater enlargement, grows visible; apex equally 

 tapered (P. polygonif.) and mostly rather sharp (P. gramin.). Also the nervation and 

 the structure are intermediate. Upper leaves stalked etc, see O. Hagström, in Neu- 

 man, Sveriges Flora 1901, 797! 



