and wings clogged by the sticky secretion, and the scent or taste would act as a deterrent to browsing animals.

Glandular Hairs

Glandular hairs sometimes take the form of papillæ, and are in many species club-shaped, or resemble largeheaded pins; they are often richly coloured, as, for instance, in some of the Currants, Geraniums, &c., glittering in sunlight like emeralds or rubies. They often develop very early, showing that they are intended to protect the young and tender leaves. In such cases they soon wither away; in others, however, they persist as long as the leaf, especially in hot and dry countries, which are particularly rich in aromatic plants.

Pleasant as is their smell-that, for instance, of the Lavender-such plants are too astringent to be eaten, and are thus protected from browsing quadrupeds.

The secretion may be either a gum, which, for instance, is richly secreted in the buds of some species of Polygonum; or a resin; or both may be present together. The resin, according to Hanstein (15), is generally secreted in the interior of the cells, and oozes through the cell wall, while the mucus is generally the product of the epidermis. The properties and functions of the two are no doubt different. Some plants secrete both, as, for instance, the Horse Chestnut.

The development of such glandular hairs in Lilac is shown in figs. 137-139. A cell raises itself somewhat above the general level of the leaf, and becomes cut off by a transverse wall (fig. 137, a, b; fig. 138, a). It then divides into two transversely, the upper cell forming the head of the pin (fig. 138, b), which may divide again by vertical and transverse walls (fig. 139).

As a general rule special hairs develop themselves into glands. In the Plane (figs. 140, 141), however, we find a remarkable combination of the two. The hairs

branch, and one fork may remain a simple pointed hair, while another develops a gland.

The glandular processes are sometimes highly developed; as, for instance, in the Rose and the Violet, where they are large and oval, one being formed at the tip of each tooth of the leaf.

In the Docks (Rumex), Polygonum, and Rhubarb (Rheum) the buds secrete a copious mucus, which in some of the larger species can even be squeezed out

in a drop. It is formed by papillary outgrowths of the epidermis.

The buds of Chilocarpus look as if they were covered by red sealing-wax (16).

(Platanus acerifolia).

An epidermal cell divides into two unequal parts by an oblique wall. The upper grows out into a 2-4-celled hair, the apical cell of which becomes a spherical gland-cell; a lateral cell grows out obliquely into a long, pointed, hair-like structure. The lower figure shows the development, the upper the perfect form of the hairs.

The case of Tabernaemontana (1, 351) is especially interesting. The buds of this plant are covered with a

gum which does not completely harden, but remains in a semi-fluid condition; and as the leaves previously covered up grow and expand, the gum remains attached to their edges, and stretches as a thin film between them. Thus the next youngest leaves are for a certain time enclosed in a small four-sided chamber, two opposide sides of which are formed by two leaves, and the other two opposite sides by a thin film of gum. The gum is eventually ruptured and the same process is repeated.

Glands are present in the axils of the leaves in the great majority of Crucifers (Norman says in nine-tenths), in most Lythrariece, and in many others.

The connection of these glands with the protection of the young and highly delicate leaf is further shown by their very early development. In fact, in some species there is a stage in which the glands are actually larger than the rudiment of the leaf itself. They are, however, often very transitory.

97

CHAPTER V

ON THE STRUCTURE OF BUDS

HAVING thus glanced at the various ways in which buds are protected by other and older structures, let us now see how they behave when they are, so to say, thrown on their own resources. In doing so I will, as far as possible, take in illustration our familiar forest trees and other common plants.

It is in some respects difficult to draw a hard-andfast line between the buds now to be considered and those described in the last chapter.

In the Whitebeam (Pyrus Aria) (fig. 125, p. 82), for instance, the pedestal of the last leaf of the previous year is persistent, and, no doubt, of some use to the very young bud; but I class it here because in the main the shelter is due to the outer, modified stipules belonging to the bud itself.

It is remarkable how many devices Nature has adopted, and how much even nearly allied groups, such, for instance, as the Willows and Poplars, differ from one another.

It is, indeed, a very general, though not invariable, rule that the outer envelopes of winter-buds are formed

H