81. FLUVIALES. 13 



Ascends to 100 or 300 yards, in England. 

 Range of mean annual temperatiu-e 51 — 47, 

 Native. Lacustral. This species would seem by the 

 records of its localities to be only sparingly scattered 

 thi'ough England, and very scarce in Scotland. The sole 

 authority for Wales, as far as my compilations of locali- 

 ties show, is Mr. Griffith, quoted in the Botanist's Guide, 

 under " Flint." For Lanarkshire there is only the au- 

 thority of Dr. Ure ; a second county in the same i)rovince, 

 Dumfriesshire, having been also reported by Mr. William 

 Stevens (Phytol. iii. 392). These two provinces are al- 

 lowed to stand among those ascertained for P. gi'amineus, 

 although it would be desirable to have them further con- 

 firmed by other botanists. For the Lake province there 

 would seem to be no antecedent improbabilitj^ ; but as it 

 rests only on the worthless testimony of Hutton, that 

 province is rejected from the area for want of admissible 

 authority. This is not the P. gramineus of Koch and 

 other Continental botanists ; on wliich see the remarks 

 under P. heterophyllus. 



1122. POTAMOGETON ACUTIFOLIUS, Link. 



IAi'ea * 2 3 4. . . . *?. 

 South limit in Sussex. 

 North limit in Norfolk, ^^c^^^^ ■ 

 Estimate of provinces 3. Estimate of counties 6. 



k Latitude 50 — 53. Local (Germ.) tj^je of distribution. 



Agrarian region. Inferagrarian zone. 

 Descends to the coast level, or nearly so, in Channel. 

 Ascends to 50 yards, less or more. 

 Range of mean annual temperature 51 — 49. 



