Leaves as the Branch's Nourishment; Four Modes of Growth
Opposite-turning leaves on brother branches, and how branchings repeat the leaf pattern
Continuing under the head SESTA, Leonardo concludes that it is the night dew, penetrating through the stalks of the great leaves, that feeds the plant and its offspring. A labelled paragraph gives the rule of leaves on the year's last branch: on two 'brother' branches they turn in contrary motion, the sixth leaf above born over the sixth below, one turning right where its companion turns left, and he calls the leaf the 'teat' of the branch and its coming fruit. A further chapter states that branches are born on the principal branches just as leaves are born on the year's shoots, in four modes of ascent: the sixth over the sixth, the two-thirds over the two-thirds, the third over the third, and the fir that grows in tiers.
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Leaves in contrary motion on brother branches (a)
On the year's last branch the leaves grow on two brother branches in contrary motion: the sixth leaf above is born over the sixth below, and where one turns toward its companion to the right, the other turns to the left. The leaf, Leonardo adds, is the teat or breast of the branch and of the fruit to be born next year.
The night dew that feeds the plant
Setting his mind to the plant's life, Leonardo recognized that the dew of the night, with its moisture, penetrates abundantly through the stalk of the great leaves to nourish the plant together with its offspring, that is, the eggs that are to produce its young.
Four modes of leaf and branch arrangement (b)
Branches are born on the principal branches just as leaves are born on the year's shoots, in four modes of one rising higher than another. The first and most universal is the sixth above over the sixth below; the second, two-thirds above over two-thirds below; the third, the third above over the third below; and the fourth is the fir, which grows in tiers.