336 24. ROSACE.E. 



where planted. The few spots m which I have chanced to 

 see it were too obviously of artificial origin to leave any 

 doubt in my own mind ; but there are or have been bota- 

 nists who hold it truly a native of this country. 



320. Dryas octopetala, Linn. 

 320,b. Dryas depressa, Bab. 



Area ********* 10 [11 * 13] * 15 16 17 18. 



South limit in Yorkshire. 



North limit in Orkney and Sutherland. 



Estimate of provinces 5. Estimate of comities 9. 



Latitude 54 — 60. Highland type of distribution. 



A. A. regions. Superagrarian — Midarctic zones. 



Descends to the coast level, in the North Highlands. 



Ascends to 900 yards, in the East Highlands. 



Range of mean annual temperature 46 — 38. 



Native. Rupestral. Occurs sparingly in Orkney, ac- 

 cording to the Rev. C. Clouston, in New Guide. In some 

 parts of Sutherland it is abundant as daisies are around 

 London. Localities occur in several of the Highland 

 counties, and also in Yorkshire ; always or mostly on lime- 

 stone formations. There is an idea with some botanists, 

 that the attachment of certain species of plants to lime- 

 stones or other peculiar rocks, is attributable to a higher 

 temperature or drier nature ; the effect of which, on the 

 plants, being nearly equivalent to that of a warmer cUme. 

 Against this view the Dryas seems an opposing fact ; since, 

 with us, it descends lower upon the limestones, both m 

 respect of elevation and latitude, than we should otherwise 

 have expected to find this arctic plant. Mr. C. C. Babing- 

 ton conjectm'ed that he had discovered a second species in 

 Ireland, and described it as such even without waiting to 



