Structure of the wood:

The wood is constituted by the following elements that appear on having given a transverse cut to a trunk of a tree:

The bark: it is the exterior cap of the tree, resects, smooth or rugose, that protects the vegetable against external aggressions. It is clear of two caps, the epidermis, that it is the most external cap, and the cork; thicker and interior cap than the epidermis. The cork changes its thickness according to the type of tree, in the banana it is thin and in the blockhead on the other hand it is gigantic.

The wood in strict sense; it exists in the elements that form the circulatory system of the plants, being the following caps:

The xilema or woody glasses; that lead the brute sap (water and mineral salts) from the roots up to the leaves.

The Floema or Líber; it is a question of embryonic wood, exists under the cork, along it there circulates the food prepared by the leaves (elaborated sap) in condition of dissolution in order that it feeds to the rest of the plant.

The cambium; it appears on the second year of growth, between the xilema and the floema, and across it the raw sap circulates. It produces in the exterior the fibrous tissue and in the interior the zone across which the sap circulates.

Whiteness; light, wood rich in sap and nourishing juices. This wood gathers the woody glasses and the floema.

Duramen; adult and compact wood usable as material of use.

Heart; senile wood, of enormous hardness, though it can be cracked.

The marrow; part that occupies the center of the shaft, it is a kind of soft and spongy wood, and has a different color from the heart. The marrow acts as backbone of the tree, from here they depart filaments towards remaining parts of the trunk. The marrow sometimes is giant, like in case of the elder, and other times it is almost imperceptible, like in case of the oak.