The Origin of our British Flora 
Here were stretches of glacial boulder-clay, which is, 
as every gardener knows, one of the most heart-breaking 
and ungenerous of soils; there perhaps bare sand with 
only a colony or two of penguins (chiefly dead) to 
improve its aridity. In another place estuarine mud, 
where the sea-lions wallowed, or great stretches of gravel 
or shingle. On the hills, bare rock and screes of rough 
stones, in the valleys a multitude of wild water-courses 
carrying destruction and death to every living plant or 
animal during the autumn or spring floods, 
There would surely be a heavy rainfall, long mournful 
weeks of cold saturating fogs; in winter a continual 
series of blinding blizzards; furious gales even in 
summer time, whilst in the higher hills there were still 
the shrunken remnants of former glaciers. It was of 
course impossible for such a country as this to be occu- 
pied straight off by our ordinary British plants, even if 
their seeds were at once available and in large quantities, 
which was not the case. The process must have been 
very slow and gradual; lichens, mosses, and arctic- 
alpines must have pioneered the way and only gradually 
extended from South to North, and from the seashore 
to the hill-tops. 
In Northern Europe (at least in Norway, Sweden, 
Denmark, Schleswig-Holstein, North Germany, and 
Prussia) four invading floras have been distinguished 
which follow after each other, and appear to be still 
proceeding northwards on the track of the retreating 
glaciers.® 
There are, first, the Dryas flora, which is a high arctic, 
or arctic-alpine, open flora such as now occurs in 
Northern Lapland; second, birch and aspen thickets ; 
third, woods of Scotch pine, and fourth, oak forests. 
As regards the Dryas flora, it consisted of, e.g., little 
dwarf willows (Salix polaris, S, herbacea, S. reticulata, 
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