FAIRY RINGS. 
239 
from the roots, which takes place only when the plant is 
in a state of living and healthy growth. Now we can 
easily understand how it is that plants of one kind will 
not flourish in the same soil for any length of time. 
When rooted in the soil, the plant continues to excrete 
or throw off certain matters which are injurious to it, or 
which have served their purpose in its economy; and the 
soil getting charged with these exudations, becomes at 
last wholly unfit for the plant which has occupied it, 
though the principles which proved obnoxious to that 
one may be nutritious and desirable for plants of another 
kind. Hence, in clearing the American woods, it is found 
that if the ground is allowed to run out of tillage, the 
vegetable tribes which formerly occupied it do not spring 
up again, but trees of another order and different con¬ 
stitution take possession of the soil; and, in the same 
manner, the salicaria flourishes in the vicinity of the 
willow, and the broom-rape in that of the hemp. 
Of plants which exercise this influence in a special 
manner, the fungi are among the most prominent; for 
wherever any of the tribe take root, they speedily render 
the soil unfit for their continued growth. The spot thus 
rendered pernicious to fungous growths is particularly 
suitable for grasses; and as the fungi disappear, grasses 
take their place in a rich and luxuriant growth. Here, 
then, is the secret of the fairy ring—the result of one 
of nature's systems of successive crops. 
To pursue the inquiry a step further, and ascertain 
why grass, in preference to other plants, should flourish 
where mushrooms decay, we have only to analyze the 
latter plant, and a solution immediately presents itself. 
