Quotation from: The Notebooks of Leonardo Da Vinci

Written by: Leonardo da Vinci

[Footnote: The two sketches of leafless trees one above another on
the left hand side of Pl. XXVII, No. 1, belong to this passage.]

396.

If the plant n grows to the thickness shown at m, its branches will
correspond [in thickness] to the junction a b in consequence of the
growth inside as well as outside.