Wood Types

Plants with true wood (wood produced from a vascular cambium) have different forms during geologic history

Origin of Wood

Secondary xylem (wood) has evolved several times during geologic history. The following details the independent origins of secondary xylem that are known from the fossil record:

Cormose lycophytes (e.g., Lepidodendron †) evolved wood in the Late Devonian
Early euphyllophytes (e.g., Armoricaphyton †) from the Early Devonian are the earliest known woody plants in the fossil record
- This plant may have given rise to woody growth in the horsetails and lignophytes
Arborescent horsetails (e.g., Calamites †) in the Mississippian
Lignophytes (e.g., Progymnosperms, Spermatophytes) in the Late Devonian

Manoxylic wood

Secondary vascular tissues with large amounts of softer storage cells (i.e., parenchyma) mixed with the wood or xylem cells (e.g., tracheids).

- The stems of these plants are softer than the wood of trees we use for lumber.
- Examples of plants with manoxylic wood are cycads, the spurs or short shoots of Ginkgo trees, as well as many extinct seed fern groups, including callistophytes †, lyginopterids †, medullosids †, Calamopityales †, and Buteoxylonales †

Pycnoxylic wood

Secondary vascular tissues with copious amounts of xylem cells (e.g., tracheids) and little parenchyma

- This wood is much stronger and more durable.
- Examples of plants with pycnoxylic wood are conifers, progymnosperms †, Cordaites †, glossopterids †, Petriellales †, angiosperms, and the long shoots of Ginkgo

Hardwoods versus softwoods

The above terms should not be confused with the terms "hard" versus "soft" woods. These terms are used by agro-foresters to make a distinction between conifer trees (softwood) and angiosperm trees (hardwood)

Conifers (mostly evergreen cone-bearing trees such as pines) have wood that is lightweight, light in color, and strong in tension, but weak in shear (along the grains). Therefore, this is called "softwood", which is usually cheaper and used for building inexpensive furniture or for paper pulp.
Flowering plants (mostly deciduous trees such as oak/maple) have wood that is darker in color, heavier in weight, and stronger in compression, tension, and shear. Therefore, this is called "hardwood", which is used to make durable furniture, flooring, and building structures

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