Bud

Bud, an undeveloped shoot or apex of an ascending axis overlapped by rudimentary leaves. Buds are mainly confined to the stems of flowering plants (Phanerogams); but an approach to this structure occurs in Chara and in ferns, whilst a few roots, such as those of the Japanese anemone (Anemone japonica) and of the birdsnest orchis (Neottia Nidus-avis), normally produce buds, and others do so when the main stem of the plant is removed. The stem of phanerogams originates in a bud, the plumule of the embryo, and as long as its growth (or that of any of its branches) continues it is terminated by a bud, the terminal or apical bud. Lateral buds are mainly produced in the axils of leaves, though only abnormally in those of floral leaves, as in Cardamine pratensis. Several buds may originate in one axil, as in the honeysuckle, or the axillary bud may be concealed within the sheathing base of the leaf, as in the plane. Buds may also originate elsewhere than in the axils, as on the cut end of a pollard tree, at any wound, or even on leaves, as in Bryophyllum (q.v.), and many "proliferous ferns," or the cut edges of Begonia leaves. Buds may become detached and reproduce the plant, as in the "cloves" produced in the axils of the scales of bulbs, or in the green bulbils in the axils of the foliage-leaves of Lilium bulbiferum, the Tiger-lily, or of the bracts of the inflorescence in some onions (Allium). Buds may develop into flowers or into leafy shoots, and in the earlier stages of their development, there is nothing to distinguish leaf-bud from flower-bud, and their future development may even be determined by appropriate cultural treatment. Thus abundant stimulating liquid food may make many buds develop into branches, the plant "running to leaf," whilst conversely a check to nutrition, such as root-pruning, may determine many young buds to become flower-buds, a flower being merely a branch with undeveloped internodes and specially modified leaves. The leaves in a bud, as a rule, grow at first more rapidly on their under surfaces (hyponasty), which causes them to arch over the growing-point. As the growth of the upper surface predominates (epinasty), they spread out horizontally. The outer leaves of buds are often hairy or viscid, as a protection against cold, and such leaves as are outermost during winter or other period of vegetative rest commonly drop off without any elongation of the internodes between them, so that each new growth of an axis has several close-set leaf-scars at its base. These deciduous bud-scales or perulae may be of various morphological origin, being sometimes leaf-sheaths, as in the gooseberry, sometimes stipules, as in the linden, and sometimes leaf-blades. The folding of the leaves in a foliage-bud is termed vernation, (q.v.); that in a flower-bud (astivation (q.v.).

Just as an entire shoot is transferred from one plant to another in the process of grafting (q.v.), so it is possible to remove a bud, or young exogenous lateral axis, uninjured from one plant, and transplant it, so to say, on to another, known as the stock, so as to bring their two cambium or growing layers into contact, when the bud will be nourished by the stock, at the same time retaining its specific character. This is termed budding. Thus any particular variety, say of Rosa damascena, may be budded on a stock of the wild briar, R. canina, retaining in the subsequent growth beyond the point of union all its characters. The bud or scion lives like a parasite on the stock. Similarly special buds or branches of plants are said to have sometimes exhibited peculiar structures by a spontaneous bud-variation, as it has been termed. The nectarine is said to have originated in this way on the peach, and the moss rose on the ordinary damask rose.