394 PRINCIPLES OF BOTANY; ETC. 
ing great drought provide it with moisture, and pro- 
tect it against the burnme solar rays. But there is 
another suil greater use of mosses, In them plants 
and trees grow as well as in the best-mould.. Mr 
Gleditsch brougiit several species of fruit to pertec- 
tion in moss alone. Some species of moss grow par- 
ticularly in marshy places, for instance, the Sphag- 
num palustre. Ponds and lakes) are often quite co- 
vered with them, and by the aid of the aquatic plants 
growing there are transformed into meadows, pas- 
tures; and after some time.into richfields.. Ac- 
cording to Tacitus the whoie Hereynian forest was 
once a marsh; at present fertile and rich meadows 
and corn fields are seen in those places described by 
that author. Old peasants im our neighbourhood 
still recollect many spots, once stagnating pools of 
water, now changed into gardens and meadows. 
The pecuhar property of mosses to imbibe a great 
deal of moisture, is the reason why they mostly 
grow in moist spots.. The summits of mountains 
are covered witii a variety of mosses, which eagerly 
imbibe all the moisture of the clouds around them. 
From ‘the very great number of clouds which com: 
monly assemble round the summits of mountains, 
and completely involve them; the mosses cannot 
keép all the water within them. It collects, there- 
fore, beneath, in the clefts of the rocks, from where 
it runs from all sides towards the lowest part, and 
there finally appears as a spring. Several of those 
combine to form a rivulet, several of which, again, 
swell to a considerable stream. We owe, therefore, 
to insignificant mosses, as they appear to be, the 
largest 
