58. =Adventitious Buds.= These are buds which certain shrubs and trees produce anywhere on the surface of the wood, especially where it has been injured. They give rise to the slender twigs which often feather the sides of great branches of our American Elms. They sometimes form on the root, which naturally is destitute of buds; they are even found upon some leaves; and they are sure to appear on the trunks and roots of Willows, Poplars, and Chestnuts, when these are wounded or mutilated. Indeed Osier-Willows are _pollarded_, or cut off, from time to time, by the cultivator, for the purpose of producing a crop of slender adventitious twigs, suitable for basket-work. Such branches, being altogether irregular, of course interfere with the natural symmetry of the tree. Another cause of irregularity, in certain trees and shrubs, is the formation of what are called [Illustration: Fig. 77. Tartarean Honeysuckle, with three accessory buds in each axil.] 59. =Accessory or Supernumerary Buds.= There are cases where two, three, or more buds spring from the axil of a leaf, instead of the single one which is ordinarily found there. Sometimes they are placed one over the other, as in the Aristolochia or Pipe-Vine, and in the Tartarean Honeysuckle (Fig. 77); also in the Honey-Locust, and in the Walnut and Butternut (Fig. 78), where the upper supernumerary bud is a good way out of the axil and above the others. And this is here stronger than the others, and grows into a branch which is considerably out of the axil, while the lower and smaller ones commonly do not grow at all. In other cases three buds stand side by side in the axil, as in the Hawthorn, and the Red Maple (Fig. 79.) If these were all to grow into branches, they would stifle each other. But some of them are commonly flower-buds: in the Red Maple, only the middle one is a leaf-bud, and it does not grow until after those on each side of it have expanded the blossoms they contain. [Illustration: Fig. 78. Butternut branch, with accessory buds, the uppermost above the axil.] [Illustration: Fig. 79. Red-Maple branch, with accessory buds placed side by side. The annular lines toward the base in this and in Fig. 72 are scars of the bud-scales, and indicate the place of the winter-bud of the preceding year.] 60. =Sorts of Buds.= It may be useful to enumerate the kinds of buds which have been described or mentioned. They are _Terminal_, when they occupy the summit of (or terminate) a stem, _Lateral_, when they are borne on the side of a stem; of which the regular kind is the _Axillary_, situated in the axil of a leaf. These are _Accessory_ or _Supernumerary_, when they are in addition to the normal solitary bud; and these are _Collateral_, when side by side; _Superposed_, when one above another; _Extra-axillary_, when they appear above the axil, as some do when superposed, and as occasionally is the case when single. _Naked buds_; those which have no protecting scales.