81. FLUVIALES. 



DISTEIBUTION OF SPECIES. 



(concluded.) 



1118. POTAMOGETON DENSUS, Linn. 



Area 1 3 3 4 5 6 7 8 * 10 11 * 13 14. 



South limit in Devon, Isle of "Wight, Kent. 



North Kmit in Haddington, Edinburgh, Lanark. 



Estimate of provinces 14. Estimate of counties 50. 



Latitude 60 — 56. English type of distribution. 



Agi'arian region. Inferagrarian — Midagi'arian zones. 



Descends to the coast level, in the Peninsida. 



Ascends to 100 or 200 yards, in England. 



Range of mean annual temperature 51 — 47. 



Native. Lacustral. As with several of the succeeding 

 sj)ecies of its genus, the provincial and comital estimates 

 are taken higher for P. densus than have hitherto been 

 shown by existing records. Partially concealed by their 

 submerged situations of gi'owth, and inconspicuous by 

 theii- flowers, the species of Potamogeton are doubtless 

 oftener overlooked, than are the gayer-coloured, or other- 

 wise more conspicuous, land plants. P. densus appears 

 to remain yet unrecorded for the humid provinces of the 

 Mersey and Lakes ; for which our records are among the 

 less complete, and in which the plant would seem more 

 likely to be present than to be absent. Accordinglj^ they 

 are reckoned in the estimate, together with various coun- 

 ties of other provinces in which the same species remains 

 still unknown, that is, not recorded in print. 

 VOL. in. c 



