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VUl 



OUTLINES OF 



47. The ajpex or summit of a leaf is 



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



ohtmc or Hunt, when it forms a very obtuse angle, or more generally when it 



is more or less rounded at the top. 



acuminate or cuspidate, "vjrhen 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 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 move decidedly indented at the end of the mid- 

 rib ; obcoTdate^ if at the same time approachiug 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. Tlie 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 what- 

 ever 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, 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 B, 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 gradually 

 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 compound, oblong or lanceolate, 

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

 skill of the describer. 



64. laeaves, when solid, Stems, Frtdts, Tubers, and other parts of plants, 

 when not flattened like ordinary leaves, are 



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



acicidar, 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 ap- 

 plied 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. 



globular or spherical^ when corresponding to orbicular in a flat surface. Round 

 applies to both. ' - 



turbinate, when shaped like a top. 



conical f when tapering upwards ; obconical, when tapering downwards, if in both 

 cases a transverse section shows a circle. 



pyramidal, when tapering upwards ; obpyramidal, when tapering downwardsf, 

 if in both cases a transverse section shows a triangle or polygon. 



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