Part I of the _Nuovo Giornale Botanico Italiano_, by Prof. G.

UZIELLI (Florence 1869, Vol. I). He remarks as to the 'four modes': "_Leonardo, come si vede nelle linie sententi da solo tre esempli. Questa ed altre inessattezze fanno desiderare, sia esaminato di nuovo il manoscritto Vaticano_". This has since been done by D. KNAPP of Tubingen, and his accurate copy has been published by H. LUDWIG, the painter. The passage in question occurs in his edition as No. 833; and there also the drawings are wanting. The space for them has been left vacant, but in the Vatican copy '_niente_' has been written on the margin; and in it, as well as in LUDWIG'S and MANZI'S edition, the text is mutilated.] four modes of growing one above another. The first, which is the most general, is that the sixth always originates over the sixth below [Footnote 8: _la sesta di sotto. "Disposizione 2/5 o 1/5. Leonardo osservo probabilmente soltanto la prima"_ (UZIELLl).]; the second is that two third ones above are over the two third ones below [Footnote 10: _terze di sotto: "Intende qui senza dubbio parlare di foglie decussate, in cui il terzo verticello e nel piano del primo"_ (UZIELLI).]; and the third way is that the third above is over the third below [Footnote 11: 3a _di sotto: "Disposizione 1/2"_ (UZIELLI).]. [Footnote: See the four sketches on the upper portion of the page reproduced as fig. 2 on P1. XXVII.] 413. A DESCRIPTION OF THE ELM. The ramification of the elm has the largest branch at the top. The first and the last but one are smaller, when the main trunk is straight. The space between the insertion of one leaf to the rest is half the extreme length of the leaf or somewhat less, for the leaves are at an interval which is about the 3rd of the width of the leaf. The elm has more leaves near the top of the boughs than at the base; and the broad [surface] of the leaves varies little as to [angle and] aspect. [Footnote: See Pl. XXVII, No. 3. Above the sketch and close under the number of the page is the word '_olmo_' (elm).] 414. In the walnut tree the leaves which are distributed on the shoots of this year are further apart from each other and more numerous in proportion as the branch from which this shoot springs is a young one. And they are inserted more closely and less in number when the shoot that bears them springs from an old branch. Its fruits are borne at the ends of the shoots. And its largest boughs are the lowest on the boughs they spring from. And this arises from the weight of its sap which is more apt to descend than to rise, and consequently the branches which spring from them and rise towards the sky are small and slender [20]; and when the shoot turns towards the sky its leaves spread out from it [at an angle] with an equal distribution of their tips; and if the shoot turns to the horizon the leaves lie flat; and this arises from the fact that leaves without exception, turn their underside to the earth [29]. The shoots are smaller in proportion as they spring nearer to the base of the bough they spring from. [Footnote: See the two sketches on Pl XXVII, No. 4. The second refers to the passage lines 20-30.] 415. OF THE INSERTION OF THE LEAVES ON THE BRANCHES. The thickness of a branch never diminishes within the space between one leaf and the next excepting by so much as the thickness of the bud which is above the leaf and this thickness is taken off from the branch above [the node] as far as the next leaf. Nature has so placed the leaves of the latest shoots of many plants that the sixth leaf is always above the first, and so on in succession, if the rule is not [accidentally] interfered with; and this occurs for two useful ends in the plant: First that as the shoot and the fruit of the following year spring from the bud or eye which lies above and in close contact with the insertion of the leaf [in the axil], the water which falls upon the shoot can run down to nourish the bud, by the drop being caught in the hollow [axil] at the insertion of the leaf. And the second advantage is, that as these shoots develop in the following year one will not cover the next below, since the 5 come forth on five different sides; and the sixth which is above the first is at some distance. 416. OF THE RAMIFICATIONS OF TREES AND THEIR FOLIAGE. The ramifications of any tree, such as the elm, are wide and slender after the manner of a hand with spread fingers, foreshortened. And these are seen in the distribution [thus]: the lower portions are seen from above; and those that are above are seen from below; and those in the middle, some from below and some from above. The upper part is the extreme [top] of this ramification and the middle portion is more foreshortened than any other of those which are turned with their tips towards you. And of those parts of the middle of the height of the tree, the longest will be towards the top of the tree and will produce a ramification like the foliage of the common willow, which grows on the banks of rivers. Other ramifications are spherical, as those of such trees as put forth their shoots and leaves in the order of the sixth being placed above the first. Others are thin and light like the willow and others. 417. You will see in the lower branches of the elder, which puts forth leaves two and two placed crosswise [at right angles] one above another, that if the stem rises straight up towards the sky this order never fails; and its largest leaves are on the thickest part of the stem and the smallest on the slenderest part, that is towards the top. But, to return to the lower branches, I say that the leaves on these are placed on them crosswise like [those on] the upper branches; and as, by the law of all leaves, they are compelled to turn their upper surface towards the sky to catch the dew at night, it is necessary that those so placed should twist round and no longer form a cross. [Footnote: See Pl. XXVII, No. 5.] 418. A leaf always turns its upper side towards the sky so that it may the better receive, on all its surface, the dew which drops gently from the atmosphere. And these leaves are so distributed on the plant as that one shall cover the other as little as possible, but shall lie alternately one above another as may be seen in the ivy which covers the walls. And this alternation serves two ends; that is, to leave intervals by which the air and sun may penetrate between them. The 2nd reason is that the drops which fall from the first leaf may fall onto the fourth or--in other trees--onto the sixth. 419. Every shoot and every fruit is produced above the insertion [in the axil] of its leaf which serves it as a mother, giving it water from the rain and moisture from the dew which falls at night from above, and often it protects them against the too great heat of the rays of the sun. LIGHT ON BRANCHES AND LEAVES (420--422). 420. That part of the body will be most illuminated which is hit by the luminous ray coming between right angles. [Footnote: See Pl. XXVIII, No. 1.] 421. Young plants have more transparent leaves and a more lustrous bark than old ones; and particularly the walnut is lighter coloured in May than in September. 422. OF THE ACCIDENTS OF COLOURING IN TREES. The accidents of colour in the foliage of trees are 4. That is: shadow, light, lustre [reflected light] and transparency. OF THE VISIBILITY OF THESE ACCIDENTS. These accidents of colour in the foliage of trees become confused at a great distance and that which has most breadth [whether light or shade, &c.] will be most conspicuous. The proportions of light and shade in a leaf (423-426). 423. OF THE SHADOWS OF A LEAF. Sometimes a leaf has three accidents [of light] that is: shade, lustre [reflected light] and transparency [transmitted light]. Thus, if the light were at _n_ as regards the leaf _s_, and the eye at _m_, it would see _a_ in full light, _b_ in shadow and _c_ transparent. 424. A leaf with a concave surface seen from the under side and up-side-down will sometimes show itself as half in shade, and half transparent. Thus, if _o p_ is the leaf and the light _m_ and the eye _n_, this will see _o_ in shadow because the light does not fall upon it between equal angles, neither on the upper nor the under side, and _p_ is lighted on the upper side and the light is transmitted to its under side. [Footnote: See Pl. XXVIII, No. 2, the upper sketch on the page. In the original they are drawn in red chalk.] 425. Although those leaves which have a polished surface are to a great extent of the same colour on the right side and on the reverse, it may happen that the side which is turned towards the atmosphere will have something of the colour of the atmosphere; and it will seem to have more of this colour of the atmosphere in proportion as the eye is nearer to it and sees it more foreshortened. And, without exception the shadows show as darker on the upper side than on the lower, from the contrast offered by the high lights which limit the shadows. The under side of the leaf, although its colour may be in itself the same as that of the upper side, shows a still finer colour--a colour that is green verging on yellow--and this happens when the leaf is placed between 426. the eye and the light which falls upon it from the opposite side. And its shadows are in the same positions as those were of the opposite side. Therefore, O Painter! when you do trees close at hand, remember that if the eye is almost under the tree you will see its leaves [some] on the upper and [some] on the under side, and the upper side will be bluer in proportion as they are seen more foreshortened, and the same leaf sometimes shows part of the right side and part of the under side, whence you must make it of two colours. Of the transparency of leaves (427-429). 427. The shadows in transparent leaves seen from the under side are the same shadows as there are on the right side of this leaf, they will show through to the underside together with lights, but the lustre [reflected light] can never show through. 428. When one green has another [green] behind it, the lustre on the leaves and their transparent [lights] show more strongly than in those which are [seen] against the brightness of the atmosphere. And if the sun illuminates the leaves without their coming between it and the eye and without the eye facing the sun, then the reflected lights and the transparent lights are very strong. It is very effective to show some branches which are low down and dark and so set off the illuminated greens which are at some distance from the dark greens seen below. That part is darkest which is nearest to the eye or which is farthest from the luminous atmosphere. 429. Never paint leaves transparent to the sun, because they are confused; and this is because on the transparency of one leaf will be seen the shadow of another leaf which is above it. This shadow has a distinct outline and a certain depth of shade and sometimes is [as much as] half or a third of the leaf which is shaded; and consequently such an arrangement is very confused and the imitation of it should be avoided. The light shines least through a leaf when it falls upon it at an acute angle. The gradations of shade and colour in leaves (430-434). 430. The shadows of plants are never black, for where the atmosphere penetrates there can never be utter darkness. 431. If the light comes from _m_ and the eye is at _n_ the eye will see the colour of the leaves _a b_ all affected by the colour of _m_ --that is of the atmosphere; and _b c_ will be seen from the under side as transparent, with a beautiful green colour verging on yellow. If _m_ is the luminous body lighting up the leaf _s_ all the eyes that see the under side of this leaf will see it of a beautiful light green, being transparent. In very many cases the positions of the leaves will be without shadow [or in full light], and their under side will be transparent and the right side lustrous [reflecting light]. 432. The willow and other similar trees, which have their boughs lopped every 3 or 4 years, put forth very straight branches, and their shadow is about the middle where these boughs spring; and towards the extreme ends they cast but little shade from having small leaves and few and slender branches. Hence the boughs which rise towards the sky will have but little shade and little relief; and the branches which are at an angle from the horizon, downwards, spring from the dark part of the shadow and grow thinner by degrees up to their ends, and these will be in strong relief, being in gradations of light against a background of shadow. That tree will have the least shadow which has the fewest branches and few leaves. 433. OF DARK LEAVES IN FRONT OF TRANSPARENT ONES. When the leaves are interposed between the light and the eye, then that which is nearest to the eye will be the darkest, and the most distant will be the lightest, not being seen against the atmosphere; and this is seen in the leaves which are away from the centre of the tree, that is towards the light. [Footnote: See Pl. XXVIII, No. 2, the lower sketch.] 434. OF THE LIGHTS ON DARK LEAVES. The lights on such leaves which are darkest, will be most near to the colour of the atmosphere that is reflected in them. And the cause of this is that the light on the illuminated portion mingles with the dark hue to compose a blue colour; and this light is produced by the blueness of the atmosphere which is reflected in the smooth surface of these leaves and adds to the blue hue which this light usually produces when it falls on dark objects. OF THE LIGHTS ON LEAVES OF A YELLOWISH GREEN. But leaves of a green verging on yellow when they reflect the atmosphere do not produce a reflection verging on blue, inasmuch as every thing which appears in a mirror takes some colour from that mirror, hence the blue of the atmosphere being reflected in the yellow of the leaf appears green, because blue and yellow mixed together make a very fine green colour, therefore the lustre of light leaves verging on yellow will be greenish yellow. A classification of trees according to their colours. 435. The trees in a landscape are of various kinds of green, inasmuch as some verge towards blackness, as firs, pines, cypresses, laurels, box and the like. Some tend to yellow such as walnuts, and pears, vines and verdure. Some are both yellowish and dark as chesnuts, holm-oak. Some turn red in autumn as the service-tree, pomegranate, vine, and cherry; and some are whitish as the willow, olive, reeds and the like. Trees are of various forms ... The proportions of light and shade in trees (436-440). 436. OF A GENERALLY DISTRIBUTED LIGHT AS LIGHTING UP TREES. That part of the trees will be seen to lie in the least dark shadow which is farthest from the earth. To prove it let _a p_ be the tree, _n b c_ the illuminated hemisphere [the sky], the under portion of the tree faces the earth _p c_, that is on the side _o_, and it faces a small part of the hemisphere at _c d_. But the highest part of the convexity a faces the greatest part of the hemisphere, that is _b c_. For this reason--and because it does not face the darkness of the earth--it is in fuller light. But if the tree has dense foliage, as the laurel, arbutus, box or holm oak, it will be different; because, although _a_ does not face the earth, it faces the dark [green] of the leaves cut up by many shadows, and this darkness is reflected onto the under sides of the leaves immediately above. Thus these trees have their darkest shadows nearest to the middle of the tree. 437. OF THE SHADOWS OF VERDURE. The shadows of verdure are always somewhat blue, and so is every shadow of every object; and they assume this hue more in proportion as they are remote from the eye, and less in proportion as they are nearer. The leaves which reflect the blue of the atmosphere always present themselves to the eye edgewise. OF THE ILLUMINATED PART OF VERDURE AND OF MOUNTAINS. The illuminated portion, at a great distance, will appear most nearly of its natural colour where the strongest light falls upon it. 438. OF TREES THAT ARE LIGHTED BY THE SUN AND BY THE ATMOSPHERE. In trees that are illuminated [both] by the sun and the atmosphere and that have leaves of a dark colour, one side will be illuminated by the atmosphere [only] and in consequence of this light will tend to blueness, while on the other side they will be illuminated by the atmosphere and the sun; and the side which the eye sees illuminated by the sun will reflect light. 439. OF DEPICTING A FOREST SCENE. The trees and plants which are most thickly branched with slender branches ought to have less dark shadow than those trees and plants which, having broader leaves, will cast more shadow. 440. ON PAINTING. In the position of the eye which sees that portion of a tree illuminated which turns towards the light, one tree will never be seen to be illuminated equally with the other. To prove this, let the eye be _c_ which sees the two trees _b d_ which are illuminated by the sun _a_; I say that this eye _c_ will not see the light in the same proportion to the shade, in one tree as in the other. Because, the tree which is nearest to the sun will display so much the stronger shadow than the more distant one, in proportion as one tree is nearer to the rays of the sun that converge to the eye than the other; &c. You see that the eye _c_ sees nothing of the tree _d_ but shadow, while the same eye _c_ sees thè tree _b_ half in light and half in shade. When a tree is seen from below, the eye sees the top of it as placed within the circle made by its boughs[23]. Remember, O Painter! that the variety of depth of shade in any one particular species of tree is in proportion to the rarity or density of their branches. [Footnote: The two lower sketches on the left of Pl XXVIII, No. 3, refer to lines 21-23. The upper sketch has apparently been effaced by Leonardo himself.] The distribution of light and shade with reference to the position of the spectator (441-443). 441. The shadows of trees placed in a landscape do not display themselves in the same position in the trees on the right hand and those on the left; still more so if the sun is to the right or left. As is proved by the 4th which says: Opaque bodies placed between the light and the eye display themselves entirely in shadow; and by the 5th: The eye when placed between the opaque body and the light sees the opaque body entirely illuminated. And by the 6th: When the eye and the opaque body are placed between darkness and light, it will be seen half in shadow and half in light. [Footnote: See the figure on the right hand side of Pl. XXVIII, No.