ORIGIN OF VEGETATION IN NITHSDALE. 5 
cept the water plants, would form a scattered open flora rooted 
in rock crevices or growing singly in sand and gravel. 
The next stage of colonisation would begin by the develop- 
ment of lichens on bare rock surface or on gravel and clay. 
These would be mostly crust lichens, such as those here exhibited. 
Soon, however, mosses would form tufts on the rock or ground 
mixed with reindeer moss and other lichens. This process is of 
great importance, because such moss tufts produce true soil in 
which worms and other insects can be found. Then various 
Arctic plants would proceed to colonise these moss carpets. The 
most important of these Arctics are Blaeberry and other Vac- 
ciniums, Sheep’s Fescue, Nardus, Deschampsia, Poa annua and 
alpina, Common Heather, Cotton Grass, certain Bushes and Deer’s 
Hair, Cloudberry, Lycopodiums. These plants would at first be 
singly planted in the moss carpet, but if things were at all favour- 
able they would very soon occupy the ground almost to the 
destruction of the moss, forming a continuous carpet or “ Blae- 
berry-Grass-Heath ’’ Association. I have not time to show how 
wonderfully these Blaeberries and Heather are adapted to do this. 
But with the appearance of this association true soil began to 
appear. The underlying rock or clay was penetrated and broken 
up by the roots, and the upper surface of the soil received regular 
supplies of leaf-mould. 
Now, as the climate became more genial, this Blaeberry- 
Grass Association would gradually creep up the valleys and hill- 
sides away from the sea until it reached the projecting points of 
Queensberry, Whitecombe, and the other storm-vexed and deso- 
late summits of the Dumfriesshire mountains. It has not yet 
completely occupied them, for the original Mountain Saxifrages, 
Oxyria, etc., still occur in ravines and rocks which are not yet 
covered by moss. 
I have found this Blaeberry-Grass-Heath on Mistylaw and 
Robber’s Craigs in Renfrewshire, and something almost identical 
is the summit flora so well described by Smith, Lewis, and others 
in Eden, Wear, Tees, and Tyne, and Yorkshire. The plants 
are for the most part identical, and all seem to be Arctic. 
If you ascend one of these hills you see no sign of man; 
nothing is visible but desolate whaup-haunted mosses and moor- 
lands stretching for miles. Indeed the cultivated and inhabited 
valleys of Dumfriesshire are exceedingly narrow, and form a very 
