NOTES ON BEITISH POTAMOGETONS 17 



*P. CooPERi Fryer (p. 61). P. cymatoides Asch. & Graeb. Syn 

 MTitteleur. Fl. i. 337 (1897). P. cymhifolius Fischer, Beit, z! 

 Kennt. Layer. Pot. in Mitt, ba^^er. Bot. Ges. 360 (1904). 



Hagstrom divides this into two forms: n. serrulatus and /3. ser- 

 ratiis : under the first he places f. eu- Coojyeri Grsiehn. (Leicestershire 

 — the only station); f. Jacksonii (Cheshire and Cambridgeshire; 

 the original record was from Yorkshire) ; and f. scoticus Hagst. — a 

 new form — from Stirling ; I have it from Salop and Notts. /^. ser- 

 ratus is only known from Bavaria. " Real P. Cooperi is besides 

 observed by us from Gudena in Denmark." 



The Irish specimens are neither of the above, being nearer per- 

 foliatus than the others, and may be called f. hihernicus : — Folia 6 cm. 

 longa, -2 cm. lata. Leaves very dark, blackish green, peduncles 4-5 cm. 

 long (^scoticus 2 cm.) ; whole plant more robust than the other forms. 



P. DENSUS L. (p. 260). Sweden in Halland; Finland, Aland 

 Isles only ; Norway at 60° n. lat. {Hart man). 



The author gives Howden, Yorksliire (1845, Storey)^ as the most 

 northern British locality ; but it occurs up to Edinburgh and Lanark. 

 Tlie varieties latifoUus Wallr., anyusfifolius M. et K., and lanci- 

 foUus Wallr., occur in Britain. The typical form is abundant on 

 Mitcham Common, Surrey. 



P. zosTEEiFOLiTJS Schum. (p. 65). Sweden to 63° n. lat. ; 

 Norway to Christiana {Blytt) ; Finland to 66° n. lat. {Hjelt) ; 

 Scotland to 56= 40' n. lat. (Forfar). 



This was referred to cuspidatus Schrad. by J. E. Smith, who of 

 course knew nothing of acutifolius Link. ; but Schrader's specimen 

 in Smith's herbarium is acutifolius. 



Hagstrom describes a f. ahortivus, w^hich he thinks "may be 

 3b hybrid with acutifolius''' : "A similar plant is also collected 

 by Babington in Scotland (hb. Stockholm) where P. acutifolius 

 is not now met with. Nevertheless it is possible that it has occurred 

 there in olden times." I do not know what this specimen is, but 

 I have little doubt it is a Rescobie one, in which the fruit is some- 

 times not developed and the flower-heads look just as they would if it 

 were a hybrid. This it is not ; in northern latitudes Potamoyeton., 

 Sparyanium, &c., often do not fruit freely in wet or cold years (see 

 Laestadius in Bid. till Kann. Vaxt. Tornea Lappmark, 1860, p. 42). 



P. ACUTIFOLIUS Link. (p. 67). Sweden to 60° 12' n. lat. 

 {Hay Strom) ; not recorded from Norway or Finland; Enyland to 

 S.E. York. {Smith herb.!). Hagstrom gives the length of the 

 peduncles as usually 10 mm. (5-23) ; in specimens from Buckenham 

 FeiTy, E. Norfolk, they are 25 mm., in those from Staines, Middlesex, 

 36 mm., but others have the normal length : neither is P. bamber- 

 yensis Fischer {acutifolius X zoster if olius). 



P. OBTUSiroLius M. & K. (p. 115). Sweden to 63'' n. lat. ; 

 'Norioay to 62° n. lat. {Blytt) ; Finland to 67"- 25' n. lat. (Wainio) ; 

 Scotland to Argyll ! and Inverness ! 



The length of the peduncles in this species is very variable ; 



in specimens from Lake Lancashire {Pear sail) they are 36 mm. 



long, four times the length of the spike. This is va^r. ffzivialis Lange 



& Mortenson, but not var. lacustris Fries, Herb. Norm. 5, no. 81 



Journal of Botant. — Vol. 57. [January, 1919.] c 



