- (1) 1. Naked seeds (gymnosperms)
- (1) 1. Palm ferns, etc. (cycadaceæ)
- (1) 2. Joint firs (gnetaceæ)
- (1) 3. Pines, firs, etc. (conifers)
- (2) 1. Fruits (angiosperms)
- (1) 1. One-seed-leaf (monocotyledons)
- 1. (1) (Bamboos, palms, grasses, etc.)
- (1) 2. Two-seed-leaf (dicotyledons)
- 1. (1) a. Herbs.
- 1. (1) b. Broad-leafed trees.
- 1. (1) (oak, ash, elm, etc.)
Conifers and broad-leaved trees are alike in that they add a new layer of wood each year which covers the old wood of root, trunk and branch. They are known as exogens—outward growers.
In woods such as the palms, bamboos, and yuccas, growth is made from within.
The new wood strands mingle with the old and cause the cross sections to appear dotted, [Fig. 218]. Trees of this class—endogens—after some years of growth form harder wood near the surface with younger and softer growth toward the center—quite the reverse of the exogens. There are no annual rings. Growth takes place mainly at the top.
Other classifications, such as deciduous, “hard woods,” “evergreens,” “soft woods,” are in common use but are not very accurate.
Fig. 218.
Deciduous trees are the broad-leaved trees and are so called because they lose their leaves in the fall. Broad-leaved trees are also called hard woods.
Conifers are called evergreens because their needle-shaped leaves remain green on the tree the year around. They are also known as soft woods.
Most of our timber is furnished by (1) the needle-leaved conifers and (2) the broad-leaved trees.