Reading a Tree's Age from Bark and Growth-Rings
Wrinkled bark near the base marks the oldest wood; the young southern side stays smooth and vigorous
The leaf finishes the three-circle argument, explaining that where the boughs touch the joint rises while the untouched middle stays low and concave. A new section (829) turns to reading a tree's age: the part nearest the trunk is oldest, shown by the wrinkles of its bark, as in walnuts where smooth new bark stretches over the old cracked bark. The years of an unmaimed tree can be counted in its principal branchings, at the growth-ring circles lettered a b c d e f taken from the branch nearest the tree's centre. Leonardo adds that the youngest part has the smoothest, cleanest bark, and that a plant's southern side shows more youth and vigour than its northern; a full leafless tree with ringed junctions is drawn in the text.
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Oldest wood near the base, read in the bark's wrinkles (n)
The part of the plant nearest its origin is oldest, shown by the wrinkles of its bark. In walnut trees a great stretch of smooth new bark often lies over the old cracked bark, so a tree holds as many ages as it has principal branchings.
Counting years in the ring-circles a b c d e f (o)
In a tree not maimed by men the years of its age can be counted in its principal branchings, at the circles a b c d e f, one at each formation of a principal branch, taking the branch nearest the middle of the tree. A tree has as many various ages as it has principal branchings.
Smooth young bark; the southern side more vigorous (p)
The youngest part of the plant has smoother, cleaner bark than any other part. The southern side of plants shows greater youth and vigour than the northern.