132 B. EH. Fernow—The Battle of the Forest. 
Though short-lived, with its light summer foliage turning into 
brilliant golden autumn hues, it gives grateful shade and pre- 
serves from the thirsty sun and wind some moisture, so that the 
better kinds may thrive and take its place when it has fulfilled 
its mission. 
One of the shrubs or half trees which first take possession 
of the soil in the western mountain country is the socalled 
mountain mahogany (Cercocarpus ledifolius) covering the bared 
slopes after the fire has killed the old timber. 
In other regions, as on the prairies of Iowa and Illinois, hazel 
bushes; or in the mountains of Pennsylvania and the Alle- 
ehenies in general, ericaceous shrubs like the laurel and rhodo- 
dendrons or hawthorn, viburnum and wild cherry are the first 
comers, while along water-courses alders and willows crowd 
even the water into narrower channels, catching the soil which 
is washed from the hillsides and increasing the land area. 
One of the most interesting soil-makers, wresting new territory 
from the ocean itself, is the mangrove along the coast of Florida. 
Not only does it reach out with its aerial roots entangling in 
their meshes whatever litter may float about and thus gradually 
building up the shore, but it pitches even its young brood into 
the advance of the battle, to wrestle with the waves and gain a 
foothold as best it may. 
Not less interesting in this respect is that denizen of the 
southern swamp, the bald cypress with its curious root excres- 
cences known as cypress knees, which, whatever their physiologic 
significance, are most helpful in expediting change of water into 
land sufficiently dry to be capable of supporting the more 
fastidious species in regard to moisture conditions. 
In passing, the remarkable adaptation to diverse conditions 
of some of the tree species should be noticed, as it gives them 
significance as geographic factors. The trees of the swamp, or 
at least many of them, seem to indicate their independence of 
moisture conditions by the range of climate and soil in which 
they are found. In fact, they grow in the swamp, not because 
that is their most suitable locality, but because they can do 
so to the exclusion of other competitors. The bald cypress itself 
will grow in the dry soil and arid atmosphere of Texas and 
Mexico; the oak which associate with it in the swamp will oc- 
cupy almost any soil.-and site; the sweet gum or liquidambar is 
found in similar places of habitat. The juniper or red cedar, 
