COMPOUND LEAVES. 



163 



stalklets of their own, nor articulated (by a joint) with the main 

 petiole, so that the pieces are at length detached and fall separately. 

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

 are so many transitions between simple and 



289. Compound leaves. These have the blade divided into entire- 

 ly separate pieces ; or, rather, they consist 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 exhibit ; and the same terms are em- 

 ployed 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 (other- 

 wise called digitate). 



290. 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 modifica- 

 tions 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 (Fig. 290), and also in the 

 Vetch tribe, where, however, the apex of the petiole is generally 



prolonged into a tendril (Fig. 287, 289). It is impari-pinnate, or 

 pinnate with an odd leaflet, when the petiole is terminated with a 



FIG. 288 - 290. Simply pinnate leaves of various forms. 



