Forest Fire Guard Stationed in a Tree
Section of a Virgin Forest
The Sequoias of California
A Forest Ranger and His Forest Cabin
Pine Which Yields Turpentine and Timber
Forest Fires Destroy Millions of Dollars Worth of Timber Every Year
Blackened Ruins of a Fire Swept Forest
Forest Management Provides for Cutting Mature Trees
Seed Beds in a Forest Nursery
Sowing Forest Seed in an Effort to Grow a New Forest
A Camping Ground in a National Forest
Good Forests Mean Good Hunting and Fishing
Young White Pine Seeded from Adjoining Pine Trees
What Some Kinds of Timber Cutting Do to a Forest
On Poor Soil Trees are More Profitable Than Farm Crops
A Forest Crop on its Way to the Market
[Transcriber’s note: “Section of a Virgin Forest” is the seventh (not the second) illustration in the book.]
HOW TREES GROW AND MULTIPLY
The trees of the forest grow by forming new layers of wood directly under the bark. Trees are held upright in the soil by means of roots which reach to a depth of many feet where the soil is loose and porous. These roots are the supports of the tree. They hold it rigidly in position. They also supply the tree with food. Through delicate hairs on the roots, they absorb soil moisture and plant food from the earth and pass them along to the tree. The body of the tree acts as a passage way through which the food and drink are conveyed to the top or crown. The crown is the place where the food is digested and the regeneration of trees effected.
The leaves contain a material known as chlorophyll, which, in the presence of light and heat, changes mineral substances into plant food. Chlorophyll gives the leaves their green color. The cells of the plant that are rich in chlorophyll have the power to convert carbonic-acid gas into carbon and oxygen. These cells combine the carbon and the soil water into chemical mixtures which are partially digested when they reach the crown of the tree. The water, containing salts, which is gathered by the roots is brought up to the leaves. Here it combines with the carbonic-acid gas taken from the air. Under the action of chlorophyll and sunlight these substances are split up, the carbon, oxygen and hydrogen being combined into plant food. It is either used immediately or stored away for future emergency.
Trees breathe somewhat like human beings. They take in oxygen and give off carbonic-acid gas. The air enters the tree through the leaves and small openings in the bark, which are easily seen in such trees as the cherry and birch. Trees breathe constantly, but they digest and assimilate food only during the day and in the presence of light. In the process of digestion and assimilation they give off oxygen in abundance, but they retain most of the carbonic acid gas, which is a plant food, and whatever part of it is not used immediately is stored up by the tree and used for its growth and development. Trees also give off their excess moisture through the leaves and bark. Otherwise they would become waterlogged during periods when the water is rising rapidly from the roots.