Rings of the growth in the wood:

The cells of the cambium form new cells that give origin to the rings of the growth. These rings can be qualified in:

Annual in the plants of the boreal zone.

Seasonal in the plants of the tropical zone with marked climatic stations.

In every ring of growth it is distinguished more or less easily:

The wood formed in spring (so called spring wood, in the annual rings, and of the first growth, in case of seasonal rings).

The wood formed in summer (summer wood, in the annual rings, and late, in the seasonal ones).

In the coniferous ones, the difference is marked basically by the color. In the leafy ones, it owes more to the group or distribution of anatomical elements (the glasses) in the ring, which produces an unequal porosity inside it, though a certain difference of color always exists, more or less marked, between the spring wood and summer wood.

In the seasonal rings of growth, the differences of porosity, owed to the distribution of glasses or thickness of the fibers' walls, correspond to the dry or rainy stations of the zone. In those in which the stations are not marked, thing that happens in many zones of the tropical forest, the differentiation of rings of growth is difficult to lead to end.