ZOOLOGY. 



THE MOUNTAIN LEPIDOPTERA OF BRITAIN: THEIR 

 DISTRIBUTION AND ITS CAUSES. 



By F. BUCHANAN WHITE, M.D., F.L.S. 

 {Continued fr 0771 p. 105). 



THE very earliest of the higher plants would be those arctic 

 or north temperate forms which grow in the immediate 

 vicinity of salt water, on the sea-shore,^ or in salt marshes ; and 

 it may be noted that some of these inhabit mountains also.^ 

 Conversely, some of the mountain plants occur on the sea-shore, 

 especially in the north. A saline element is necessary for the 

 species restricted to the vicinity of the sea, but those common 

 to sea-shore and mountain inhabit these localities, not entirely 

 by choice, but because they have been driven out of the more 

 favoured intermediate ground to less crowded situations, or at 

 least into situations in which their constitutions enable them to 

 hold their own against other plants. For the same reason some 

 of the mountain plants descend and some of the maritime plants 

 ascend along the shingly or sandy margins of rivers, where they 

 have usually less of a crowd to contend with. This is one of 

 the reasons why we find some of the so-called maritime plants 

 high up on the mountains, their presence having been at one 

 time considered to afford a proof of the theory that these moun- 

 tains were once islands in an iceberg-laden sea. 



Amongst the first plants to occupy the dry bed of the German 

 Ocean would be the various species that followed closest on the 

 retreating ice-sheet (viz., the arctic and arctic-alpine), but they, 

 at least in the southern part, would soon be crowded out by the 

 plants that followed. We may have some idea of the order in 

 which the species would grow if we study the sequence in which 

 our wild plants occupy any portion of ground recently made ' 



^ E.g.^ AIe7'te7tsia 7na7-iti7na, Psa77i77ia haltica, and, in a less degree, yu7icus 

 lalticus. 



- Such as Arf7ie7-ia, Flatitago, and Silene^ /iia7-iti77ia, Cairx inciu-vata, &c. 



