81. FLUVIALES. 17 



North limit in Moraj', Aberdeen, Westmoreland. 



Estimate of in'o^inces 10. Estimate of counties 20. 



Latitude 51 — 58. Germanic (?) type of distribution. 



Agi-arian region. Inferagi'arian — Superagi'arian zones. 



Descends to the coast level, in Thames province. 



Ascends to 400 yards, in Humber province. 



Range of mean annual temperature 49 — 43. 



Native. Lacustral. Only of late years distinguished 

 fi-'om P. lucens ; and its distribution is j)robably more ex- 

 tended, and less interrupted, than would ajjpear from the 

 area above indicated. Mr. James Backhouse reports 

 (Phytol. i. 1126) that he found it in Malham Tarn, York- 

 shii'e, with P. perfoliatus ; and as the altitude of that tarn 

 is said to exceed 1200 feet, the altitude above mentioned 

 is given for the upper limit of the species. On the 

 Western side of Britain, my notes show it rex^oi-ted from 

 two counties only, Stafford (Rev. R. C. Douglas) and West- 

 moreland (Mv. Borrer) ; while there are a dozen counties 

 of the eastern j)rovinces in which it has been found. I 

 have a specimen from the Botanical Society of Edin- 

 bm-gh, gathered in Forfarshii-e, by Professor Balfoui-, but 

 mis-labelled "rufescens." Indeed, about half a dozen of 

 our species of this genus have been rej)eatedly mis-named 

 and cross-named on the printed labels of that Society. 



1128. POTAMOGETON LONGIFOLIUS, Gay. 



Area [12]. 



Incognit, or Hiberiaian. Said to have been found in 

 Rydal Water, Westmoreland, and in Lough Carrib, Gal- 

 way, Ireland. Mr. Borrer has ascertained that the plant 

 of Westmoreland is P. heterophyllus (Phj'tol. ii. 426) ; 

 and Mr. Thomas Kirk suggests that the Galway plant 

 may really be P. lucens. 



VOL. ni. D 



