wooden productsWood, in the strict sense, is yielded bytrees, which increase indiameterby the formation, between the existing wood and the innerbark, of new woody layers which envelop the entire stem, living branches, and roots. This process is known assecondary growth; it is the result of cell division in thevascular cambium, a lateral meristem, and subsequent expansion of the new cells. Where there are clear seasons, growth can occur in a discrete annual or seasonal pattern, leading togrowth rings; these can usually be most clearly seen on the end of a log, but are also visible on the other surfaces. If these seasons are annual these growth rings are referred to as annual rings. Where there is no seasonal difference growth rings are likely to be indistinct or absent.If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season is then known as the latewood or summerwood.[5]However, there are major differences, depending on the kind of wood (see below).