180 J. O. HAGSTEOM, CRITICAL EESEAECHES ON THE POTAMOGETONS. 



»P. fluitans; P. ohlongus sec. Fries.* On the contrary the specimens from »Eke- 

 bergi), coll. 1854, C. A. W (= C. A. Wbsterlund), Hartm. Handb. Skand. Fl., 

 12th ed., 1889, 45, are P. iwlygonifolius v. amphibius Fries. Gothland, several sta- 

 tions: Fleringe and Bunge, the nothernmost localities of Europe, Rute, Westerhejde, 

 Ardre, Bal etc., gathered by different collectors, the oldest specimens by Lonnroth, 

 1853, and Elmquist also in 1853 (hb. Stockholm., Uppsal., Lund, et Gothob.). 



Denmark, many stations in the islands; locus classicus is »Oxeniose prope Hof- 

 mansgave Fioniae, ubi primum invenit celeberrimus M. Vaiild: Hoeman Bang in hb. 



— England in Kent, Cambridgeshire, Norfolk, Yorkshire and westward in Hereford- 

 shire (hb. Stockholm., Uppsal., Lund.). — Holland, (see Vuyck, Revisie etc. 1895!). 

 Belgium, Tirlemont, Tiiielens (hb. Stockholm.), Middelkerk, Crbpin (hb. Stockholm.). 



— Germany: Hannover to Baden (hb. Stockholm., Uppsal., Luird.). — Switzerland, 

 Geneva, Ayassb (hb. Uppsak, Lund.), Oerlikon, 81, Buser and others (hb. Stock- 

 holm., Uppsal., Lund.). — Austria, Moosbriinn (Nieder Ost.), 76 Wiesbatjr (hb. 

 Stockholm., Uppsal.), Bohemia, Lissa, Celakovsky (hb. Lund.), Hungary, Altofen, 

 Steinitz (hb. Lund.). — Greece, according to Graebner, Potatnog. 1907, 69 (not 

 1912). — France, manj^ stations (hb. Stockholm., Uppsal., Lund.). ■ — Spain, Ojos 

 del Guadiana (La Mancha), 83, Nilsson (hb. Uppsal.). — Italy, Genoa, 42, Deho- 

 TARis (hb. Stockholm., Lund.), Sardinia, 81, Reverchon (hb. Stockholm., Uppsal., 

 Lund.), Sicily, leg. Lojacone (hb. Stockholm.) and Citarda (hb. Stockholm.). 



The species is also recorded from North Africa (Algeria), Arabia and Australia, 

 but I have not seen specimens from there. Norwegian specimens (Arendal: Blytt, 

 1897) are undoubtedly mistaken for P. folygonifolius Pourr. 



As is shown above the distribution area of this species is, on the whole, the 

 same as that of P. polygonifolius but it does not spread so far towards the north 

 and westward, and seems also to choose a more calcareous ground (cf. the occurrence 

 of the two species in the Scandinavian peninsula!). 



P. coloratiis Vahl x polygonifolius Pourr. (P. angliciis n. hybr,). 



Folia submersa sat longe petiolata; natantia subcoriacea, ad nervaturam ut 

 in P. colorato. Color ad basin caulis rufus ut in P. polygonifolio. 



Although P. coloratus and polygonif. are so closely connected one to another, 

 yet nobody has observed any crossing between them. Some specimens from Woking 

 Heath in Surrey, England, gathered by Ar. Bennett in 1881, however, seem to me 

 in all probability to be such a bastard. The colour is reddish; submersed leaves 

 pretty long-petioled ; floating leaves scarcely coriaceous; ligules rather long (influences 

 from P. polygonif.). On the other hand the nervation of the floating leaves resembles 

 that of P. coloratus with more distant longitudinal nerves. Of all specimens from 

 different countries I have seen, these are the only ones occupj'ing a position that 

 makes me presume a hybrid origin. Yet I ought to add that I have not seen P. colo- 

 ratus from any place in Surrey, but it is growing in the neighbouring Kent (see 

 above!). 



