PEAT BOGS. - lix 
on, whilst decomposition proceeds apace under the 
action of bacteria, fungi, and the smaller animals. 
This decomposition differs from decay on exposed 
lands, owing to the water-logged soil shutting out 
the atmosphere, and humic and organic acids are 
formed, which act as preservatives. The White Moss 
between St. Andrews and Holm is one of the best 
examples of a boggy peat moss in Orkney. The 
surface is too wet for Caluna vulgaris to grow with 
any vigour. It is there in abundance, but conditions 
are unfavourable for its successful growth, owing to 
the sodden nature of the soil. The surface consists 
mainly of slightly rounded, hummocky braes, with 
low interspaces, where sphagnum grows in abund- 
ance. These sphagna are always soaking with water, 
as, owing to the flat surface, there is no drainage. 
The sphagnum is like a sponge—it not only retains 
the water for a long time against drought, but it 
extracts moisture from the dew and mist present 
during fog and dewfall. It is rather curious to find 
Drosera—both rotundofolia and Anglica—in great 
abundance in the water-logged depressions among 
the sphagnum. 
ECOLOGY. 
Quite a new branch of botanical science has been 
introduced in the last decade, viz., the study of plant 
associations. Kcology bears the same relation to 
botany that sociology does to humanity. Both are 
comparatively new subjects, and are now receiving 
much attention and study. In a general way the 
communities that plants form have been known for 
