EFFECT OF SETTLEMENT UPON INDIGENOUS VEGETATION. 187 
above the beech. It may live long in this way, but it succumbs 
ultimately in the fight—of old age if of nothing else, for the life of 
the birch in Denmark is shorter than that of the beech. The 
writer believes that light (or rather shade) is the cause of the 
superiority of the latter, for it has a greater development of its 
branches than the birch, which is more open, and thus allows the 
rays of the sun to pass through to the soil below, while the tufted 
bushy tops of the beech preserves a deep shade at its base. Hardly 
any young plants can grow under the shade of the beech except 
its own shoots ; and while the beech can flourish under the shade 
of the birch, the latter dies immediately under the beech.”* He 
goes on to show that the order of succession of trees in Danish 
forests has been aspen, birch, fir, oak and beech. 
Something of the same kind is going on in our own land on the 
slopes of Mount Kembla. There may be seen a thick under- 
growth of Acacia, Hugenia, and many other brush plants, while 
towering above them are huge blackbutts (Hucalyptus pilularis ), 
dead to the smallest twigs. Twenty years ago there were many 
of the blackbutts distributed about among the brush, and the 
smaller trees have all been cut down and converted into mining 
timber, but the big trees, left untouched on account of their un- 
wieldiness, have not survived the destruction of their companions. 
Probably the clearing away of the forest trees, which before 
allowed a certain amount of light and heat to reach the soil, has 
permitted the scrubby growth to spring up thickly, and this cuts 
off the light from the soil and so causes it to become colder and 
wetter. The gums left then suffer from this, and gradually die 
off as described by Forbes in the passage before quoted. I can- 
not account for the deaths of these giants in any other way. 
These passages all tend to show that a new flora arises when 
land is deforested. So far, the subject has not been thoroughly 
investigated in Australia, but there is evidence that something of 
the kind does take place. In the Mudgee district for example, 
* Darwinism, Cheap Ed., p. 20, et seq. 
