NATURAL SELECTION. | X1x 
is flat and raised very little above sea-level. Near 
the lighthouse on the north end is a bit of natural 
heath on which are found a few plants, which were 
doubtless more abundant before the extensive culti- 
vation of pasture-land. Some of these were difficult 
to naine off-hand, as they presented unnatural appear- 
ances. St. John’s wort—Hypericum pulchrum—was 
so prostrated by exposure to high winds that at first 
it looked like a new variety. Then Potentilla tor- 
mentilla had the same appearance, being flattened to 
the earth as if it were a creeping plant. This was 
more prominent there than elsewhere ; but through- 
out the islands the evidence of strong prevailing 
winds is clearly visible. On all the hills, especially 
on the west and north-west sides, the heather is 
prostrated in the direction of the prevailing winds. 
There are two temperature problems which are 
ready to upset the calculations of a botanist. Our 
winter climate is milder than that of any other 
county in Scotland, and our summer is colder than 
any other—Shetland excepted, whose flora our owr 
very much resembles. Veronica decussata, an ever- 
ereen, grows well when sheltered from high winds. 
The winter of 1911 was mild and free from the 
high winds of former years. Two plants which had 
grown into bushes of over four feet in my garden 
produced one year many perfect flowers in January. 
The following year they were again in a well- 
advanced state when a continuance of gales tor 
about four days blasted the buds ready to. burst. 
Fuchsia Magellanica flowers well in Orkney, and 
in July is covered with its red and purple bell- 
