Fast eBooks

Hence it
follows, that the abundance of red clover and wild heart's-ease in a
district will depend on a good supply of cats to kill the mice, which
would otherwise destroy and keep down the humble-bees and prevent them
from fertilising the flowers. A chain of connection has thus been found
between such totally distinct organisms as flesh-eating mammalia and
sweet-smelling flowers, the abundance or scarcity of the one closely
corresponding to that of the other!
The following account of the struggle between trees in the forests of
Denmark, from the researches of M. Hansten-Blangsted, strikingly
illustrates our subject.[8] The chief combatants are the beech and the
birch, the former being everywhere successful in its invasions. Forests
composed wholly of birch are now only found in sterile, sandy tracts;
everywhere else the trees are mixed, and wherever the soil is favourable
the beech rapidly drives out the birch. The latter loses its branches at
the touch of the beech, and devotes all its strength to the upper part
where it towers above the beech.


Pages:
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61