Ix. ] ABOUT MOSSES AND LICHENS. 143 
ate especially in fallow fields, where the soil is thin 
and not retentive of moisture, especially in calcareous 
districts, Within a square yard half-a-dozen species 
may sometimes be found when these conditions 
exist. Though at a moderate distance from the sea 
a variety of species may occasionally be found in 
great perfection, there are very few which, like Schzs- 
tidium maritimum, choose by preference situations 
constantly exposed to the spray of salt water” (Ber- 
keley). 
On the fernery they should be encouraged, not 
_only for the sake of their own beauty, which is great, 
_but as helping to prevent the excessive evaporation 
of moisture from the soil, and conducting the mois- 
ture from the atmosphere. They form a suitable 
nidus for fern-spores to fall upon, affording them the 
requisite conditions to induce germination. They 
also serve to prepare hard soils for more deeply-root- 
ing plants, and for this reason are among the most 
valuable of Nature’s pioneers, covering the hard rocks 
with a soft coating of delicate green. Their tiny 
rootlets break up the surface of the rock, and their 
dead bodies gradually form a thick stratum of vege- 
table mould, still covered by the younger living 
individuals. Here the wind-borne seeds of the giant 
pines and firs find a resting-place, and, germinating, 
send their long roots down into the fissures of the 
rock for support, and absorb their nourishment from 
the moss-made mould. And in this way Nature 
covers up the bare rocks with the most beautiful of 
mantles, that of living greenery, and always the 
mosses and liverworts and lichens are the humble 
