168 THE LEAVES. 



in the middle, is said to be retuse, or, if more strongly notched, 

 emarginate (Fig. 188) : an obovate leaf with a wider and more 

 conspicuous notch at the apex is termed obcordate (Fig. 190), 

 being a cordate or heart-shaped leaf inverted. When the apex is, 

 as it were, cut off by a straight transverse line, the leaf is said to 

 be truncate : when abruptly terminated by a small projecting 

 point, it is mucronate (Fig. 188, 189) : and when an acute leaf has 

 a narrowed and prolonged apex, or tapers to a point, it is acumi- 

 nate, or pointed, as in Fig. 191. 



287. All these terms are equally applicable to expanded sur- 

 faces of every kind, such as petals, sepals, &c. : and those terms 

 which are used to describe the modifications of solid bodies, such 

 as stems and stalks, are equally applicable to leaves when they 

 affect similar shapes, as they sometimes do. 



288. The whole account, thus far, relates to SIMPLE LEAVES, 

 namely, to those which have a blade of one piece, however cleft 

 or lobed, or, if divided, where the separate portions are neither 

 raised on stalklets of their own, nor articulated (by a joint) with 

 the main petiole, so that the pieces are at length detached from it. 

 The distinction, however, cannot be very strictly maintained ; there 

 are so many transitions between simple and 



289. Compound Leaves (Fig. 211, 215-221). These have the 

 blade divided into entirely separate pieces ; or, rather, they con- 

 sist of a number of blades, borne on a common petiole, usually 

 supported on stalklets of their own, between which and the main 

 petiole an articulation or joint is formed, more or less distinctly. 

 These separate blades are called LEAFLETS : they present all the 

 diversities of form, outline, or division, which simple leaves ex- 

 hibit ; and the same terms are employed in characterizing them. 

 Having the same nature and origin as the lobes or segments of 

 simple leaves, they are arranged in the same ways on the common 

 petiole. Compound leaves accordingly occur under two general 

 forms, the pinnate, and the palmate, otherwise called digitate. 

 The pinnate form is produced when a leaf of the pinnately veined 

 sort becomes compound ; that is, the leaflets are situated along the 

 sides of the common petiole. There are several modifications of 

 the pinnate leaf. It is abruptly pinnate, when the leaflets are 

 even in number, and none is borne on the very apex of the petiole 

 or its branches, as in Cassia ; and also in the Vetch tribe, where, 

 however, the apex of the petiole is generally prolonged into a ten- 



