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Some portions of the heath had, however, been
enclosed a few years before, and these enclosures were crowded with
young fir-trees growing too close together for all to live; and these
were not sown or planted, nothing having been done to the ground beyond
enclosing it so as to keep out cattle. On ascertaining this, Mr. Darwin
was so much surprised that he searched among the heather in the
unenclosed parts, and there he found multitudes of little trees and
seedlings which had been perpetually browsed down by the cattle. In one
square yard, at a point about a hundred yards from one of the old clumps
of firs, he counted thirty-two little trees, and one of them had
twenty-six rings of growth, showing that it had for many years tried to
raise its head above the stems of the heather and had failed. Yet this
heath was very extensive and very barren, and, as Mr. Darwin remarks, no
one would ever have imagined that cattle would have so closely and so
effectually searched it for food.
In the case of animals, the competition and struggle are more obvious.


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