OUTLINES OF BOTANY. XIX 



below the middle, an:"! tapering to a point ; a linear-ohlong one is scarcely narrow 

 enough to be called linear, yet too narrow to be strictly oblong, and does not 

 conspicuously taper either towards the summit or towards the base. 

 47. The apex or summit of a leaf is 



acute or pointed, when it forms an acute angle or tapers to a point. 



obtuse or blunt, when it forms a very obtuse angle, or more generally w T hen 

 it is more or less rounded at the top. 



acuminate or cuspidate, when suddenly narrowed at the top, and then 

 more or less prolonged into an acumen or point, which may be acute or obtuse, 

 linear or tapering. Some botanists make a slight difference between the acu- 

 minate and cuspidate apex, the acumen being more distinct from the rest of the 

 leaf in the latter case than in the former ; but in general the two terms are used 

 in the same sense, some preferring the one and some the other. 



truncate, when the end is cut off square. 



retuse, when very obtuse or truncate, and slightly indented. 



emarginate or notched, when more decidedly indented at the end of the 

 midrib ; obewdate, if at the same time approaching the shape of a heart with 

 its point downwards. 



mucronate, when the midrib is produced beyond the apex in the form of 

 a small point. 



aristate, when the point is fine like a hair. 



48. The base of the leaf is liable to the same variations of form as the apex, 

 but the terms more commonly used are tapering or narrowed for acute and 

 acuminate, rounded for obtuse, and cordate for emarginate. In all cases the 

 petiole or point of attachment prevent any such absolute termination at the 

 base as at the apex. 



49. A leaf may be cordate at the base whatever be its length or breadth, or 

 whatever the shape of the two lateral lobes, called auricles (or little ears), 

 formed by the indenture or notch, but the term cordiform or heart-shaped leaf 

 is restricted to an ovate and acute leaf, cordate at the base, with rounded 

 auricles. The word auricles is more particularly used as applied to sessile and 

 stem-clasping leaves. 



50. If the auricles are pointed, the leaf is more particularly called auriculate ; 

 it is moreover said to be sagittate, when the points are directed downwards, 

 compared to an arrow-head ; hastate, w r hen tbe points diverge horizontally, 

 compared to a halbert. 



51. A reniform leaf is broader than long, slightly but broadly cordate at the 

 base, w r ith rounded auricles, compared to a kidney. 



52. In a peltate leaf, the stalk, instead of proceeding from the lower edge of 

 the blade, is attached to the under surface, usually near the lovver edge, but 

 sometimes in the very centre of the blade. The peltate leaf has usually several 

 principal nerves radiating from the point of attachment, being, in fact, a cor- 

 date leaf, with the auricles united. 



53. All these modifications of division and form in the leaf pass so gradually 

 one into the other that it is often difficult to say which term is the most appli- 

 cable — whether the leaf be toothed or lobed, divided or compound, oblong or 

 lanceolate, obtuse or acute, etc. The choice of the most apt expression will 

 depend on the skill of the describer. 



54. Leaves, when solid, Stems, Fruits, Tubers, and other parts of 

 plants, when not flattened like ordinary leaves, are 



setaceous or capillary, when very slender like bristles or hairs. 



acicular, when very slender, but stiff and pointed like needles. 



subulate, when rather thicker and firmer like awls. 



linear, when at least four times as long as thick ; oblong, when from about 

 two to about four times as long as thick, the terms having the same sense as 

 when applied to flat surfaces. 



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