XX OUTLINES OF BOTANY. 



more or less prolonged into an acumen or paint, which may be acute or ob- 

 tuse, linear or tapering. Some botanists make a slight difference between 

 the acuminate 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 ; obcordate, 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 prevents 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 auri- 

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

 downwards, compared to an arrow-head ; hastate, when the points diverge 

 horizontally, compared to a halbert. 



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

 at the base, with 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 lower 

 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 cordate leaf with the auricles united. 



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

 dually one into the other that it is often difficult to say which term is the 

 most applicable — whether the leaf be toothed or lobed, divided or com- 

 pound, 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. 



ovoid, when egg-shaped, with the broad end downwards ; obovoid, if the 

 broad end is upwards : these terms corresponding to ovate and obovate 

 shapes in flat surfaces. 



