•Exogenous trees grow for only part of the year. Having remained dormant during the winter, the spring brings the rising of the sap.
•The roots absorb moisture and minerals from the soil and this fluid flows up the tree underneath the bark to the leaves. The rising of the sap develops the first half layer of a new annual growth ring.
•At the close of the summer, when the sap descends, further growth results. This latter, outer portion of the annual ring, termed 'autumn wood', is readily distinguishable from 'spring wood' as it is some what lighter in color.
Woods