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. [Illustration: 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. [Illustration: 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). [Illustration: Fig. 128-132. Various forms of radiate-veined leaves.]