54 PRACTICAL FORESTRY 
canopy may be most conducive to soil betterment 
and rapid growth. 
The sandiest soil, the barest rock, and even shal- 
low lagoons, if situated in a congenial climate, and 
not interfered with by mankind or other preventive 
agencies, will in time become fit for forest-growth. 
In the case of shallow lagoons, the work begins with 
aquatic plants of many sorts, which gradually cause 
the formation of soil. The water-hyacinth in many 
parts of the world, especially in Florida, has so 
clogged even the rivers that navigation has been 
seriously impeded. Swamps on the edges of shallow 
lakes and ponds are fringed by a zone of pioneer 
aquatic plants. On sandy soils and rocks the low 
lichens, mosses, and herbs first play their part; then 
bushes and shrubs; then the less exacting of trees, 
such as the pines; and finally, when the soil has 
reached sufficient depth and fertility, the climax for- 
est, consisting of rich hardwoods, such as oaks and 
beeches, with a few conifers, such as hemlock, is in 
time produced. By the excessive removal of forest 
litter and the reckless destruction of the forest by 
fire, the process is reversed. The work of centuries 
is quickly undone, and the soil is left in the form of 
sterile, shifting sand, or barren rock. Forests should 
be grown on poor soil, because it will be constantly 
improved under their influence. When agricultural 
