8 INTEODTrCTION". 



falsely compared to a matberaatical Une, for a linear leaf has always a per- 

 ceptible breadth. When uot broader than thick, it is caUed subulate, com- 

 pared to an awl. 



lanceolate, when about tliree or more times as long as broad, broadest 

 below the middle, and tapering towards the summit, compared to the head 

 of a lance. 



cuneate, when broadest above the middle, and tapering towards the 

 base, compared to a wedge with the point downwards. 



spathulate, when the broad part near tlie top is short, and the narrow- 

 tapering part long, compared to a spatula, or fiat ladle. 



ohlong, when from about two to nearly four times as long as broad. 



ovate, when scarcely twice as long as broad, and rather broader below 

 the middle, compared to the longitudinal section of an egg ; ohovate is the 

 same form, with the broadest part above the middle. 



orhicular, oval, or elliptical, when compared to the mathematical circle, 

 oval, or ellipsis. 



transversely ohlong, vrhen conspicuously broader than long. 

 Intermediate forms between any two of the above are expressed by com- 

 bining two terms. A linear-lanceolate leaf is long and narrow, yet broader 

 below the middle and tapering to the point ; a linear-oblong one is scarcely 

 narrow enough to be called linear, yet too broad to be strictly oblong, and 

 does not conspicuously taper either towards the summit or towards the 

 base. 



The apex or summit of a leaf, the end furthest from the petiole, is 



acute, or pointed, when it forms what mathematicians call an acute 

 angle, or tapers to a point. 



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

 when it is more or less rounded at the top, without forming a mathematical 

 angle. 



acuminate, or cuspidate, when suddenly naiTOwed near the top, and then 

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

 obtuse, linear or tapering. Some botanists make a shght difference be- 

 tween the acuminate and cuspidate apex, but in general tliey are used in the 

 same sense, some preferring one term 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. 



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. 

 The base of the leaf is hable to the same variations of form as the apex, 

 but tlie 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 the point of attachment prevent any such absolute termination at 

 the base as at the apex. 



A leaf may be cordate at the base whatever be its length or breath, or 

 whatever tlie 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 apphed to sessile 

 and stem-clasping leaves. 



If the auricles are pointed, the leaf is said to be sagittate when the points 



