SURFACE 



179 



By the outline of the leaf, v>e refer to the general form of its margin, 

 whether that be entire, or not. If not, then the general form of an 

 outline is determined by connecting the extreme points of its margin 

 with one another (Fig. 486, an obovate outline) . It matters not, there- 

 fore, whether a leaf be entire, toothed, lobed, or parted, or even if it be 

 entirely compound or decompound, its outline will be the same, pro- 

 vided a line connecting its extreme marginal points with one another 

 possess a given form. The forms of leaves on this basis may be divided 

 into three general classes — (a) those broadest at or about the middle, 

 (b) those broadest at some point above the middle, (c) those broadest 

 at some point below the middle. 



.^<y^. 





'"'"fcfa? '\ 



1,1 ^'^^r^f UQ 



Fig. 484. A bullate upper surface. 485. A cancellate lower surface. 



Of the first class, beginning with the narrowest, v,e have theC^apillary_ 

 or Hair-like form s, the Filiform or Thread-shaped (Fig. 491), the^Acerose 

 or Needle-shaped _(Fig. 492), as those of the pine, and the Li near or 

 R ibbon-shaped, (Fig. 487), all of which are so elongated that they 

 present the appearance of being about of uniform width throughout. 



A leaf similar to but shorter than the linear, in proportion to its 

 breadth, without regard to the character of its apex or base, is Oblong__ 

 (Fig. 488). 



One of similar form, but having a length of not more than twice or 

 thrice its breadth, and narrower than a circle, is Oval_XFigs. 489 and 

 490), a term which must not be confounded Avith(Ovate^ 



If an oblong or an oval leaf possess a regularly rounded outline into 

 and through the apical and basal portions, it is called Elliptical. We 

 have, therefore, two forms of the eUiptical leaf, denominated respectively 

 Oblong-Elliptical (Fig. 488) and Oval-Elliptical (Fig. 489). 



