Mosses and Peat 
when soaked in water, will be at once refreshed and 
revived ; the leaves open out and stretch themselves, and 
the whole plant becomes fresh and vigorous. 
A square yard of the feathery green Hypnum mosses 
will absorb in one minute fully one pound of water. 
But its capacity for drinking water is very small when 
compared with the regular peat moss (Sphagnum), A 
square yard of Sphagnum, after it has been saturated, 
will yield by careful drying 10,700 grs. of water." 
So that it is clearly impossible for mossy stones or 
moss-covered rocks to be worn away by rain. When 
the mossy cushion is saturated, the water simply flows 
over the top of it without ever reaching the stone. 
Such moss carpets would seem also to protect the rock 
against weathering by frost action, at least to some 
extent, for moss is a bad conductor of heat. 
Moss cushions and moss carpets are very interesting, 
and have much more importance than one would sup- 
pose. In some of those found on dry walls, the little 
stems are closely packed and upright. When one looks 
down on them with a lens, one sees at once how perfect 
they are when considered as rain anddust traps. Their 
reddish brown rhizoids are closely entangled, and full 
of fine soil with insects’ eggs, relicts of insect life, worms, 
&c., interspersed in it. That soil is good and rich; it 
is not peat, and so if the germinating rootlet of a grass 
manages to grow down to it through the moss cushion, 
it will branch luxuriantly and a vigorous little grass seed- 
ling will soon display its green rapidly growing leaves 
against the beautiful velvety background of the moss. 
This colonisation happens more frequently with the 
other type of moss cushion in which the moss stems 
form a successive series of curved feathery branched 
sprays thrown out from the centre and lying flat upon 
one another. These Hypnoid cushions are much larger 
71 
