202 Botany

plants, and that they are poor in lime, potash and
phosphorus. The water of a bog too, is strongly acid,
and as a rule much colder than that of a swamp. The
acid character is due doubtless to the absence of lime.
Thus bog soceities, though growing where water is
plentiful, are of an entirely different character from
those of the swamp. The plants of such soceities are
rather xerophytic in character. They have a diminished

IMAGE
Bog, Steward Island =

power of root absorpion and must therefore provide
against excessive transpiration. Several reasons have
been assigned for this peculiarity, none of which
is entirely satisfactory. It is said, for instance, that the
excessive coldness of bog water tends to check absorpt-
tion, while it is also alleged that the presence of acids
and certain mineral salts has a similar effect.In the
true bog, bog-moss or sphagnum as a rule forms the
basis of the plant society. This is by some said to be
due to the fact that sphagnum, unlike most plants