The bud may either be protected by older organs, or its own outer envelopes may be modified for the purpose.

In some plants, especially those which are quick

B

FIG. 2.-BEGONIA.

A, shoot seen from above. B, shoot seen from one side. Reduced.

growing or natives of tropical countries, the buds are comparatively naked and unprotected. Even in the tropics, however, though protection is not needed against cold, it is required against the burning sunlight and against drought.

In the Begonias (fig. 2), for instance, as Mr. Potter has pointed out (1),' the buds are shaded from the overpowering heat of the sun by the older leaves. Plants grown under artificial conditions do not show the arrange

FIG. 3.

FIG. 4.

-B

YOUNG LEAVES OF HYPERICUM CALYCINUM. Nat. size. FIG. 3, seen from the side. FIG. 4, with one leaf turned back to show the younger, enclosed pair (B).

ment well, as the leaves are often drawn to one side or the other by the light. But Mr. Potter, who has had the opportunity of examining many species in a wild state, found that they were always more or less arranged as shown in fig. 2.

The works referred to by these numbers (1, &c.) are given in the 'Bibliography' at the end of the book.

The figure also shows how admirably the peculiar form of the leaf is adapted to their mode of growth. In many other plants also the leaves, as they develop, successively protect the younger ones.

A somewhat similar case is afforded by Uvaria (figs. 105, 106, p. 70); and also by common Rhubarb,

where the delicate new leaves in the centre of the plant are protected by the large, horizontally spreading, older ones.

Figs. 3 and 4 show the arrangement in one of the St. John's Worts (Hypericum calycinum). Each pair of opposite leaves is at first apposed by their edges,

which touch all the way round, leaving between them an almond-shaped space, in which the next pair are enclosed; they in their turn surround the third, and

so on.

Mesembryanthemum blandum has the leaves opposite, triquetrous, 3-5 cm. long, rounded on the dorsal edge, very shallowly grooved on the upper surface,

FIG. 7.-LEAF OF PLANE (Platanus), showing mode of protection of the young bud.

more decidedly so at the base, and connate there, forming a sheath 3-5 cm. long, which remains green after the stem it encloses has become ripened and brown. The middle line of the sheath--that is, the line of junction of the two leaves-becomes brown with age while the thicker portion is still green.

In other plants, as in Stachys (fig. 6), the leaves

do not fit so closely, but the protection is enhanced by numerous hairs.

In the Plane (fig. 7) the base of the leaf-stalk is hollowed out, forming a sort of cup or extinguisher, which completely covers the young bud. By the time the leaf drops the outer envelopes of the bud are suf

UNOPENED BUDS OF NORWAY MAPLE. Enlarged.

FIG. 8 shows a leaf-bud. FIG. 9 is also a flower-bud.

ficiently developed and strengthened to protect the young and delicate leaves within.

In Monocotyledons it is a general rule that the bases of the leaves enclose and well protect the bud.

Though leaves and flowers come out with a surprising burst of vegetation in suitable spring weather, their development is slow and gradual. The summer