Leaves considered with regard to the manner in which they succeed each other in aifferent stages of the plant.

1. Seminal, leaves which come up with the plant when it first appears above the surface of the earth; as in the garden bean; these leaves are only the cotyledons, or lobes of the seed, which, after nourishing the young plant, decay.

2. Primordial, leaves growing immediately after the seminal leaves, and resembling them in position, form, and size. The primordial leaf, according to the fanciful idea of a French botanist, is a sketch which nature makes before the perfection of her work.

3. Characteristic, leaves which are found in the mature state of the plant; or according to the idea above advanced, nature, in them, perfects her design.

It is not always, however, that this process, with regard to change of leaves, takes place; as in many cases, the proper, or characteristic leaf, is the only one which appears.

Form of Leaves.

The form of the leaf is expressed by various terms borrowed from the names of different objects; as palmate, hand-shaped; digitate, from digitus, the finger, &c. We will illustrate some of the most common forms of simple leaves, leaving you to consult the vocabulary for many terms, which it would be too tedious to attempt to define in the body of this work.

Orbicular, or the round leaf; the Nasturtion affords an example of this kind, (See Fig. 38, a ;) this is also peltate, having its petiole inserted into the centre of the leaf, and thus resembling a shield.

Reniform, (from the Latin ren, the kidney,) or as it is sometimes called kidney-form; the Ground-ivy (Glechoma) has a leaf of this kind, (See Fig. 38, b;) it is crenate, or has a margin with scalloped divisions; ciliate, being fringed with hairs, like eyelashes.

Cordate, (from the Latin cor, the heart,) or heart-shaped. Fig. 38, c, represents a cordate leaf with an acuminated point, that is, acute and turned to one side; the margin is serrated, or notched like the teeth of a saw; this kind of leaf may be seen in the Aster cordifolium, or aster with a heart-shaped leaf.

Fig. 39.

Ovate, obovate, oval; these are

terms derived from

d the Latin ovum, an

egg; suppose the figure at 39, a, to

represent an egg; you observe that one end is broader than the other; now, if to this broad end you add a petiole, prolonging it into Leaves with respect to succession-Form of Leaves-Orbicular-Reniform-Cordate-Ovate-Obovate-Oval.

a mid-rib with some lateral divisions, you have, as at b, the representation of an ovate leaf. If the petiole were placed at the narrowest end, it would be an obovate leaf. An oval leaf (c,) is when both the ends are of equal breadth. When the length is much greater than the breadth, the leaf is said to be elliptical, as at d.

Deltoid, from the Greek letter, delta A; this kind of leaf is represented at e, Fig. 40; the Lombardy poplar affords an example of the

Sagittate (from sagitta an arrow,) or arrow-shaped leaf; this is represented at a, Fig. 41; the Sagittaria, an aquatic plant, affords an example of this leaf.

Acerose, or needleshaped; this is represented at b, Fig. 41. Leaves of this kind are mostly clustered together, as in the pine; they are subulate, or pointed like a shoemaker's awl; they are rigid and evergreen.

Trees with acerose leaves, are usually natives of mountainous or northern regions; any other kind of leaves would, in these situations, be overpowered by the weight of snow, or the violence of tempests; but these admit the snow and wind through

Elliptical--Lanceolate-Linear-Sagittate-Acerose.

their interstices. Their many points and edges, presented even to a gentle breeze, produce a deep solemn murmur in the forest; and when the storm is abroad and the tempest high,

"The loud wind through the forest wakes,

With sound like ocean's roaring, wild and deep,

And in yon gloomy pines strange music makes."

Burns, in describing such a scene, says; "this is my best season for devotion: my mind is wrapt up in a kind of enthusiasm to Him, who 'walks on the wings of the wind.""

Pinnatifid, may be seen at Fig. 41, d; leaves of this form are sometimes finely divided, like the teeth of a comb; they are then said to be pectinate.

Lyrate, differs from pinnatifid in having its terminating segment broader and more circular. (See Fig. 41, c.)

Fig. 42.

Palmate, or hand shaped, (Fig. 42, a;) one species of the passion flower (Passiflora cærulea) affords a good example of this kind of leaf. The oblong segments, like fingers, arise

from a space near the petiole, which may be considered

Digitate, or fingered leaf (Fig. 42, b,) differs from the palmate in having no space resembling the palm of a hand; but several distinct leafets arise immediately from the petiole, as may be seen in the Horse Chestnut.

Connate, (Fig. 42, c;) the bases of opposite leaves are united so as to appear one entire leaf.

Pinnatifid-Lyrate-Palmate-Digitate-Connate-Lobed.

Sinuate, from the Latin sinus, a bay; this term is applied to leaves

which have their margins indented with deep roundish divisions, as the leaf at b, Fig. 43.

Emarginate, denotes a slighter indentation, as the leaf at c, Fig. 43.

Flabelliform, or fan-shaped, (from fabellum, a fan ;) this form of the leaf is seen in some of the palms. In China they are used for fans, and sold to foreign merchants for the same purpose. Fig. 44 is a representation of the dwarf fanpalm.

Stellated, or whorled, (from stella, a start ;) this term is applied both to leaves and flowers, and relates to the manner in which they grow around the stem, as in Fig. 45.

Tubular: there are many varieties of this kind; the leaf of the onion is a complete tube. The Sarracenia or side-saddle flower has the sides of its leaf united, forming a cup which is found filled with liquid, supposed to be a secretion from the vessels of the plant. In some countries of the torrid zone is the wild pine, (Tillandsia,) the leaves of which are hollowed out at their base, so as to be capable of containing more than a pint of fluid. A traveller says, "by making an incision into the base of this leaf, and collecting in our hats the water which it contained, we could obtain a sufficient, supply for the relief of the most intense thirst." This water is not a secretion from the plant, but is deposited during the rainy season.

The pitcherplant (Nepenthes distillatoria, Fig. 46,) affords a most singular, tubular appendage, to its lanceolate leaf; beyond the apex

of the leaf a, the mid-rib extends in the form of a tendril; at the extremity of this tendril is the cylindrical cup or pitcher b, about six inches in length and one and a half in diameter; it is furnished with a lid, c, which opens and shuts with changes in the atmosphere. The cup is usually found filled with pure water, supposed to be a secretion from the plant. Insects which creep into it are drowned in the liquid, except a small species of shrimp, which lives by feeding on the Sinuate Emarginate-Flabelliform-Stellated-Tubular.

rest.

The pitcher-plant is a native of Ceylon, where it is called monkey-cup, on account of its being frequented by these animals for the purpose of quenching their thirst.

Compound Leaves.-When several leafets grow on one petiole, the whole is termed a compound leaf, as in the rose.

Pinnate; Fig. 47, a, represents the petiole or principal leaf stalk bearing leafets arranged opposite to each other; these may be either petioled or sessile. b, b, represent the stipules, the whole taken together forms one compound pinnate leaf. The term pinnate is from the Latin pinna, a wing or pinion.

Binate; when two leafets only spring from the petiole, as in Fig.

47, c.

Decompound, when a pinnate leaf is again divided, or has its leaves

twice compound, as Fig. 49, a. At b, is a representation of tri-compound leaves.

We shall now add some miscellaneous examples of various kinds of

leaves for the examination of the

Fig. 50 at a, is a leaf of the Ilex aquifolium, (holly ;) it is oval and dentate, with spinescent teeth.

b, is a leaf of the Malva crispa, (mallows;) it is seven-lobed, crisped or irregularly platted, and finely crenulate.

c, is a leaf of the Hydrocotyle tridentata; it is cuneiform, dentate at the summit.

d, is a leaf of the Corchorus japonicus; it is oval-acuminate, doubly denticulate.

Compound

leaves-Pinnate-Binate-Ternate-Biternate-Triternate-Decom

pound-Size of leaves-Explain Fig. 50.