than the leaf. By the time, however, that the leaf-blade has reachedth inch (fig. 67) the stipules have caught it up. They are more oval, more pointed, and bordered by a row of small projections. They continue to grow (fig. 68) more rapidly than the leaf-blade, and somewhat unequally (fig. 69), the larger one becoming rather more (fig. 70), the shorter one rather less, than double as long as the leaf-blade. Then comes a somewhat abrupt transition, and the outer scales do not, of course, correspond to stages in the development of a normal leaf. A rudimentary leaf, such as that in fig. 70, is followed by a scale of quite a different form: broader, wrapping round the bud, and consisting of three parts nearly but not quite equal in length, and separated almost to the base (fig. 71); the two outer pieces representing the stipules are rather broader than the central. In the next (fig. 72) the leaf-blade is rather longer than the stipules, and the common stalk or leaf-base is longer in proportion. This is still more the case in the next two (figs. 73, 74). In the twelfth (fig. 75) the leaf-stalk is abruptly truncated; and in the following the stalk and stipules are reduced to three small prominences. Finally, the outer scale is much shorter and broader in proportion (fig. 79).

THE TULIP TREE (Liriodendron tulipifera)

In the Tulip Tree the leaf commences as a slight projection immediately below the growing-point, and

81

gradually widens into a ridge, the two ends of which eventually meet, forming a ring.

One part raises itself above the rest and forms the leaf-stalk; the two side pieces become the stipules. They grow upwards and inwards, finally forming a hood over the growing-point. About the time when

82

TULIP TREE (Liriodendron tulipifera).

FIG. 80.-Very young leaf and stipule, x 20. FIG. 81.-Do. do. second stage, × 20. FIG. 82.-Do. do. rather more advanced stage, × 20.

the stipules meet the leaf-blade commences. It is at first a very narrow, delicate, hyaline membrane. The bud then assumes the appearance shown in fig. 80.

The next stage (fig. 81) shows the growth of the leaf-blade, which is more developed in fig. 82. Fig. 17, p. 14, shows how closely the young leaf fits in the

hollow of the bud; while the final arrangement of the leaf in the bud is shown in figs. 17 and 18.

In the axillary buds, as a rule, the outer covering consists of two stipules, the rest of the leaf not being developed (fig. 83). Sometimes, however, at the base a small projection may be seen (fig. 84), which is a

0000

83

84

FIGS. 83-86.-TULIP TREE.

rudiment of a petiole.

85

86

Outlines of different axillary buds.

Sometimes this is rather more developed (fig. 85), and sometimes a rudimentary blade also appears (fig. 86).

The reversal of the leaf in the bud, owing to the length and early development of the petiole, is very unusual. In Amicia Zygomeris the leaf is bent, but only forms a right angle with the petiole.

ROSE

The leaf of the Rose (see ante, fig. 58, p. 46) is more complicated. It commences as a small knob at the side of, and immediately below, the growing-point. When this knob has reached a certain length it presents two lobes (fig. 87), which arise almost simultaneously. The upper of these becomes one of the

1 According to Schacht, however, the stipule appears first.

upper leaflets, the lower is one of the stipules. Almost immediately a third, and then a fourth, lobe make their appearance. The third is the rudiment of a leaflet of the second pair, the fourth of the third.

Thus the stipule appears almost simultaneously with the first and upper leaflet, before any of the lower

FIG. 87.-GROWING-POINT OF ROSE WITH TWO LEAVES IN SUCCESSIVE STAGES OF DEVELOPMENT. Highly magnified.

and later ones. These originate close above the stipules. Gradually, however, the petiole elongates, thus carrying the lower leaflets away from the stipule. De Candolle described the stipules as being connate

with the petiole. This, however, is not, I think, strictly correct. The true petiole is the leaf-stalk above the stipules. The winged part below is really a development of the leaf-base.

Adnate stipules, as these are called, arising from a similar development of the leaf-base, occur in many

FIG. 88. SECTION ACROSS THE BUD OF A ROSE. A, growing-point; L', youngest leaf; L2, three folded lobes of second leaf; St", stipules of second leaf; Sc'-Sc', scales.

other cases, as, for instance, in some Lupins, Clovers, Potentilla, &c. That winged petioles are not always stipular is, however, shown by the case of Lathyrus; for instance, L. silvestris.