FORMS OF POTAMOGETON NEW TO BRITAIN 173 



from twelve others. In fruit the heads of fruits are closely agglo- 

 merated around the peduncle, and very interrupted. 



Other references to it will be found in Hjelt, Consp. Fl. Fennica, 

 547 (1895) ; Le Jolis in Mem. Soc. Nat. Cherbourg, xxvii. 294 

 (1891) ; Asch. & Graebn. Syn. Fl. Mittel-eur. i. 351 (1897). 



2. P. gracilis Wolfg. ex Roem. & Schultes. " Caule fluitante, 

 gracili, simplicissimo, debili ; foliis omnibus submersis, alternis, 

 remotis, membranaceis, tenuissimus, oblongis lineari-lanceolatisve, 

 obtusiusculis, sessilibus, utrinque attenuatis ; pedunculis longis- 

 simis, filiformibus ; spica brevi, cylindrica, pauciflora. Wolfg. MS. 

 n. 14. Besser in litt." Wolfgang in Roem. & Schult. Syst. Mant. 

 iii. 355 (1827). 



P. borealis Kihlman ex Bot. Notiser, 1887. 84. 



P. Wolfgang* Kihlman, Herb. Fennica, 34, 128 (1889). 



P. salicifolius /3 lanceolatus Hartm. Skand. Fl. ed.xi. 432 (1879). 



P. gramineus f. Wolfgangii Neuman & Ahlfvengren, Sveriges FL 



796 (1901). 

 P. alpinm x gramineus Aschers. & Graebn. Fl. Mitt.-eur. i. 328 



(1897). 

 Distribution. Europe: Finland, in ten provinces. Russia 

 (Ingria). Sweden (Sundberg sp. ?). Pomerania (Erlangen). Lithu- 

 ania. Eastern Siberia, Merck in herb. Steven {Wolfg. 1. c). Ada: 

 Mongolia, Ordos (Potaninl ex Maximowicz). Japan (Faurie \). 

 America: Canada, Lake Hannah, Ontario (J. Macoun !). Great 

 Britain: u England 1" Aschers. & Graebn. I.e. Ireland: Co. West- 

 meath and Longford, in the River Inny, July, 1885 (R. M. Bar- 

 rington I). 



3. X P. Tiselii Richter PL Europ. i. 13 (1890). P. graminea 

 X nutans Tis. in Hartm. Hand. Skand. Fl. ed. 12, 48 (1889). 



Sweden: Bjorkgren (Tiselius sp.). Denmark: Gudena in Jyll- 

 andia (Baagoe sp.). Ireland: Co. Westmeath and Longford. In 

 the River Inny (Barrington sp.). 



The specimens accord well with the Danish ones, but not so well 

 with the Swedish. Ascherson and Graebner (op. cit. p. 333) make 

 two forms of this : A. per-gramineus, B. per-natans. 



I have some doubt whether the Swedish and Danish specimens 

 really belong to the same form. This was recorded doubtfully as 

 P.ftuitans Roth in Irish Top. Bot. 318 (1901). 



4. P. nitens Weber var. maximus rmhi. This is the plant we 

 have been naming var. latifolius Tis. non Fieber, Pot. Boh. 30 

 (1838). Fieber's plant is simply the type of Weber's nitens, and 

 Tiselius's name will not hold. In some states this comes in habit 

 and appearance near to perfoliatns L. 



I have seen specimens from East Perth (Sturrock), MidEbudes 

 (S. M. Macvicar), and Kerry {Scully). 



5. P. pusillus L. var. acuminatus mihi. In 1892 Messrs. Kid- 

 ston and Stirling sent me two sheets of specimens named <4 P. 

 acutifolius Link." They were gathered on the Forth and Clyde 

 Canal in Stirlingshire, June 30th, 1891. They do not belong to 

 Link's species, but it is not easy to place them. In habit they are 



