_The chapters composing this portion of the work consist of observations on Form, Light and Shade in Plants, and particularly in Trees summed up in certain general rules by which the author intends to guide the artist in the pictorial representation of landscape._ _With these the first principles of a_ Theory of Landscape painting _are laid down--a theory as profoundly thought out in its main lines as it is lucidly worked out in its details. In reading these chapters the conviction is irresistible that such a_ Botany for painters _is or ought to be of similar importance in the practice of painting as the principles of the Proportions and Movements of the human figure_ i. e. Anatomy for painters. _There can be no doubt that Leonardo, in laying down these rules, did not intend to write on Botany in the proper scientific sense--his own researches on that subject have no place here; it need only be observed that they are easily distinguished by their character and contents from those which are here collected and arranged under the title 'Botany for painters'. In some cases where this division might appear doubtful,--as for instance in No._ 402--_the Painter is directly addressed and enjoined to take the rule to heart as of special importance in his art._ _The original materials are principally derived from MS._ G, _in which we often find this subject treated on several pages in succession without any of that intermixture of other matters, which is so frequent in Leonardo's writings. This MS., too, is one of the latest; when it was written, the great painter was already more than sixty years of age, so we can scarcely doubt that he regarded all he wrote as his final views on the subject. And the same remark applies to the chapters from MSS._ E _and_ M _which were also written between_ 1513--15.