The Elements of Botany, For Beginners and For Schools. Gray Asa
said to be Palmately or Digitately veined, or (since the ribs diverge like rays from a centre) Radiate-veined.
133. Since the general outline of leaves accords with the framework or skeleton, it is plain that feather-veined (or penni-veined) leaves will incline to elongated shapes, or at least to be longer than broad; while in radiate-veined leaves more rounded forms are to be expected. A glance at the following figures shows this.
Fig. 115–120. A series of shapes of feather-veined leaves.
134. Forms of Leaves as to General Outline. It is necessary to give names to the principal shapes, and to define them rather precisely, since they afford easy marks for distinguishing species. The same terms are used for all other flattened parts as well, such as petals; so that they make up a great part of the descriptive language of Botany. It will be a good exercise for young students to look up leaves answering to these names and definitions. Beginning with the narrower and proceeding to the broadest forms, a leaf is said to be
Linear (Fig. 115), when narrow, several times longer than wide, and of the same breadth throughout.
Lanceolate, or Lance-shaped, when conspicuously longer than wide, and tapering upwards (Fig. 116), or both upwards and downwards.
Oblong (Fig. 117), when nearly twice or thrice as long as broad.
Elliptical (Fig. 118) is oblong with a flowing outline, the two ends alike in width.
Oval is the same as broadly elliptical, or elliptical with the breadth considerably more than half the length.
Ovate (Fig. 119), when the outline is like a section of a hen's egg lengthwise, the broader end downward.
Orbicular, or Rotund (Fig. 132), circular in outline, or nearly so.
Fig. 121, oblanceolate; 122, spatulate; 123, obovate; and 124, wedge-shaped, feather-veined, leaves.
135. A leaf which tapers toward the base instead of toward the apex may be
Oblanceolate (Fig. 121) when of the lance-shaped form, only more tapering toward the base than in the opposite direction.
Spatulate (Fig. 122) when more rounded above, but tapering thence to a narrow base, like an old-fashioned spatula.
Obovate (Fig. 123) or inversely ovate, that is, ovate with the narrower end down.
Cuneate or Cuneiform, that is, Wedge-shaped (Fig. 124), broad above and tapering by nearly straight lines to an acute angle at the base.
Fig. 125, sagittate; 126, auriculate; and 127, halberd-shaped or hastate leaves.
136. As to the Base, its shape characterizes several forms, such as
Cordate or Heart-shaped (Fig. 120, 129), when a leaf of an ovate form, or something like it, has the outline of its rounded base turned in (forming a notch or sinus) where the stalk is attached.
Reniform, or Kidney-shaped (Fig. 131), like the last, only rounder and broader than long.
Auriculate, or Eared, having a pair of small and blunt projections, or ears, at the base, as in one species of Magnolia (Fig. 126).
Sagittate, or arrow-shaped, where such ears are acute and turned downwards, while the main body of the blade tapers upwards to a point, as in the common Sagittaria or Arrow-head, and in the Arrow-leaved Polygonum (Fig. 125).
Hastate, or Halberd-shaped, when such lobes at the base point outwards, giving the shape of the halberd of the olden time, as in another Polygonum (Fig. 127).
Peltate, or Shield-shaped (Fig. 132), is the name applied to a curious modification of the leaf, commonly of a rounded form, where the footstalk is attached to the lower surface, instead of the base, and therefore is naturally likened to a shield borne by the outstretched arm. The common Watershield, the Nelumbium, and the White Water-lily, and also the Mandrake, exhibit this sort of leaf. On comparing the shield-shaped leaf of the common Marsh Pennywort (Fig. 132) with that of another common species (Fig. 130), it is at once seen that a shield-shaped leaf is like a kidney-shaped (Fig. 130, 131) or other rounded leaf, with the margins at the base brought together and united.
137. As to the Apex, the following terms express the principal variations:—
Acuminate, Pointed, or Taper-pointed, when the summit is more or less prolonged into a narrowed or tapering point; as in Fig. 133.
Acute, ending in an acute angle or not prolonged point; Fig. 134.
Obtuse, with a blunt or rounded apex; as in Fig. 135, etc.
Truncate, with the end as if cut off square; as in Fig. 136.
Retuse, with rounded summit slightly indented, forming a very shallow notch, as in Fig. 137.
Emarginate, or Notched, indented at the end more decidedly; as in Fig. 138.
Obcordate, that is, inversely heart-shaped, where an obovate leaf is more deeply notched at the end (Fig. 139), as in White Clover and Wood-sorrel; so as to resemble a cordate leaf inverted.