THE PLANTS OF THE GRAMPIANS. 243 
mountains,—lower in the deep and dark valleys in the midst 
of a tract of mountains, than in the more open valleys or 
plains about their outskirts, — lower among shaded rocks, 
than on the more gradual declivities,—lower near the sea- 
coast, than in places more inland. ese differences appa- 
rently depend chiefly upon the cooler summer temperature 
and more humid atmosphere of such spots as tend to pro- 
duce alpine plants at inferior elevations. But all alpine 
species have not an equal tendency to descend into dark 
valleys or along the courses of streams, or to grow upon 
shaded rocks or near the sea shore. The consequence is, 
that in such situations several species are occasionally found 
far below others, with which they are naturally associated by 
climate, when they grow in similar situations ; and their abso- 
lute altitude thus becomes an imperfect guide to their true 
relative positions as determined by climate. 
n example of these shangen of altitude, we may take 
The former is often seen 
eg the latter, as we ascend the moory hills about the more 
central and inland portions of the Grampians ; but the latter 
having a greater aptitude for growing among rocks, about the 
beds of streams, and in maritime places, it may in these 
latter situations be found several hundred feet below the 
localities of Azalea procumbens on open summits or decliyities 
at no great distance. So likewise, on the inland hills of the 
Grampian chain, we often see Gnaphalium supinum and Epi- 
lobium alpinum, commencing nearly together, at several hun- 
dred feet of eleyation; yet the latter is reported to have 
travelled down the course of the Dee, so low as to be now 
found established by the side of that river, near the coast 
town of Aberdeen. On the Grampians, also, Dryas octope- 
tala is found only on rocks upwards of two thousand feet 
above the sea, while Juncus triglumis occurs as low as seven- 
teen or eighteen hundred feet. Yet in the north of Sutber- 
land, the Dryas may be seen abundantly on cliffs and moors, 
almost down to the sea level, while I am not aware that 
Juncus triglumis ever occurs so low. 
T2 
