4. By making the buds unpalatable or inaccessible to insects.

5. By toning down the light.

In some cases, as in Mullein (Verbascum), the whole plant is covered with felted hairs.

In the Wayfaring Tree (Viburnum Lantana) (fig. 186, p. 118) the outer leaves of the bud protect the inner, but they all develop, and suffer very little from the cold, as they are protected by a thick coat of stellate hairs, which cross and intercross, thus forming a sort of grey felt. In the Dogwood (Cornus sanguinea), Buckthorn (Rhamnus Frangula), and others, the young leaves are similarly protected. In the Vine, again, the bud is covered only by a felt of hairs.

Lastly, in some plants, as in the Horse Chestnut (Esculus Hippocastanum) and Plane (Platanus), some of the scales protecting the bud are hairy.

In the Plane (Platanus) the stipules are connate, the upper part being turned over in a sort of frill, so that they almost resemble a green flower, from the centre of which the stalk emerges (fig. 136). If the base of the leaf-stalk be examined, it will be found, as we have already seen, to form a regular cap, protecting the bud. After the leaves have fallen the winter-buds are covered by several cap-like stipules (see figs. 263–268), the leaves belonging to which have become completely aborted. The outer stipule or cap is brown or reddish brown, and secretes a gummy substance on its inner sur

face, besmearing the bud as in the Horse Chestnut, but only in the very early stages. As the bud swells the outer cap becomes ruptured, and appears then like a deeply concave scale, which is glabrous, or nearly so.

This

is followed by others, which attain a somewhat larger size before the expanding bud causes them to split; they are densely covered with brown hairs externally and glabrous internally.

In the Horse Chestnut the fur is on the young leaves themselves. In this species, as in many others, the hairs drop off when the leaf expands and their function is fulfilled.

Virgilia lutea and Gym

nocladus, both members of Leguminosa, and Pterocarya, an ally of the Walnut, may be mentioned as other cases in which the bud is well protected by furry hairs.

Protection by Stiff Hairs

In many cases, as, for instance, in the common Stachys (S. sylvatica) (fig. 6, p. 5) and its allies, the bud is protected by stiff hairs.

In certain species such hairs contain an acrid liquid, as in the Common Nettle (Urtica dioica).

Protection by stiff hairs occurs also among the Labiata in Galeopsis (G. Tetrahit and versicolor); among the Boragineæ in Echium, Lycopsis, Borago, Anchusa; among the Loase in Loasa; among the Leguminosa in Mucuna; Saxifragea in Davidsonia; Malpighiacea in Malpighia, &c.

These hairs constitute, however, a protection to the plant as a whole, rather than to the buds specially.

Protection by Gum, Resin, or Turpentine

In other cases buds are protected by gummy or resinous secretions, as in the Horse Chestnut (Esculus), the Poplar (Populus), Hazel Nut (Corylus), Honeysuckle (Lonicera), Currant (Ribes), Lilac (Syringa), Hornbeam (Carpinus), Elder (Sambucus), and Alder (Alnus), in many herbaceous plants (Viola, Helianthus, Salvia), and most Conifers.

The gum is often confined to the outer surface, the interspaces between the leaves being filled by hairs.

The gum or resin is secreted by hairs, by glands, by leaf-teeth, or by the general epidermis. The gum cells are generally developed early, and are short-lived. The secretion lessens transpiration, and in many cases also serves to protect the young leaves from insects and other animals. Smaller insects would get legs

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