of the two has its back to the main stem it is often much smaller than the outer one.

PROTECTION BY STIPULES

In by far the larger number of cases stipules protect

P

FIG. 188.-SHOOT OF LEEA COCCINEA.

P, petiole of leaf, the lamina being cut off; S, stipule; L, young leaf emerging from stipules.

the younger leaves only, but in some species they develop early, and cover their own leaf-blades.

This is the case, for instance, in the Pea (fig. 26, p. 23) and the Hop (Humulus Lupulus) (figs. 47, 48, p. 34). In the Vine, again, the stipules are large, and appear

some time before the leaves, covering the whole bud (figs. 127, 128, p. 84). They fall early.

In Leea (L. coccinea), another member of the Vine family, the same thing occurs; they are also (fig. 188) large, and enclose the whole bud, but they are persistent.

In the allied genera, Cissus, and Ampelopsis (Virginian Creeper) (fig. 189), the stipules also cover their own leaf-blades.

In Bucklandia populnea (fig. 190), a Himalayan plant.

which belongs to the Hamamelidea (the Witch Hazel family), the stipules are large, oval, unequal-sided, and cohere at the edges, thus forming an almond-shaped box, within which the leaf is developed. The petiole elon

gates greatly, and becomes twice bent, as shown in the figure, so that the leaf remains erect. This arrangement is, so far as I know, unique.

In the Passion Flower (Passiflora racemosa) the stipules are large, foliaceous, and developed far in advance of their own leaves, so that each pair enclose their own leaf, the simple tendril in its axil, and the younger portion of the bud. Proceeding from the outside inwards, the stipules change considerably, being first ovate, gradually becoming smaller, then lanceolate, and finally subulate. In some other species of Passiflora the stipules more or less completely protect the bud, and the petioles are terete, and are provided with glands.

In by far the greater number of cases, however, stipules protect the younger leaves only.

In the Willows, as we have already seen, the stipules develop late, and the bud is protected by a pair of modified leaves. In the allied genus, Populus (the Poplar), on the contrary, the stipules develop early, and to them the protection of the bud is entrusted.

In the Black Poplar (Populus nigra) the terminal bud (fig. 191) is conical and somewhat angular.

The first and second pairs of scales (fig. 192), forming part of the terminal bud, are stipules belonging to leaves that developed during the previous summer and fell in autumn. They only cover, however, a part of the bud. They are the hardest of the

POPULUS NIGRA, VAR. PYRAMIDALIS, x 2. WINTER-BUDS.

FIG. 191.-Terminal bud showing one pair of persistent stipules, st, st, belonging to a leaf of a previous season.

FIG. 192.-Terminal bud showing one from each of two pairs of persistent stipules, st', st".

FIG. 193.-Axillary bud showing only one of the outer pair of stipules, st.

FIG. 194.-7, third leaf in the bud, often dying in winter; st, st, its stipules shown separately above.

FIG. 195.-7, fifth leaf in the bud; st, st, its stipules.

FIG. 196.-The same shown separately.

FIG. 197.-1, eighth leaf in the bud; st, st, its stipules.

FIG. 198.-, outer face of eighth leaf; st, st, its stipules spread out.