KERNS AND MOSSES. 13 
The adaptation of plants to their respective positions, 
and the effects which their decay and renovation pro- 
gressively occasion, are beautifully exemplified in the Bog- 
moss (Sphagnum}. 
This plant is fully developed in peaty swamps, and 
becomes, like the heath, a social plant ; or, in other words, 
it obtains exclusive possession of the ground, and lives in 
society. Such monopolies, however, are happily of rare 
occurrence, being checked by various causes ; for not only 
are many species endowed with equal powers of appro- 
priating similar stations, but each plant, for reasons not yet 
fully ascertained, renders the soil where it has grown less 
fitted for the support of ' ' other individuals of its own 
species, or even other species of the same family." Yet the 
tract, though occupied, it may be, by two or three usurping 
brotherhoods who, to the exclusion of many others, are 
enabled throughout long periods to maintain their ground 
successfully against intruders, if even impoverishing it for 
themselves is yet, by an irrefragable law of nature, im- 
proved for plants of another family. The tract thus appro- 
priated may be an extensive moor, or a lofty mountain ; 
a sandy waste, or well- watered plain ; subject to equal 
diversity of soil or climate : still the operating causes which 
enable certain plants to maintain their ground against all 
others is equally developed, and the effects are everywhere 
the same. Oaks, for instance, render the sites whereon they 
grow more fertile for the fir tribe, and firs prepare the soil for 
the reception of acorns or sapling oaks, which thrive well. 
Every agriculturist, as Lyell justly observes in his " Prin- 
ciples of Geology," feels the force of this law of the organic 
world, and regulates accordingly the rotation of his 
crops. 
The Bog-moss above mentioned, instead of deteriorating 
its place of growth, seems to have thrown a mantle over 
vast denuded tracts and unpeopled regions, preserving many 
a giant oak or pine that would otherwise have crumbled to 
