1G4 THE LEAVES. 



leaflet (Fig. 281, 288). There are some subordinate modifications; 

 such as lyrately pinnate, when the blade of a lyrate leaf (Fig. 278) 

 is completely divided, as in Fig. 285 ; and interruptedly pinnate, 

 when some minute leaflets are irregularly intermixed with larger 

 ones, as is also shown to some extent in the figure last cited. The 

 number of leaflets varies from a great number to veiy few. When 

 reduced to a small number, such a leaf is said to be pinnately seven-, 

 or five-, or tri-foliolate, as the case may be. A pinnate leaf of three 

 or five leaflets is often called ternate or quinate ; which term-, how- 

 ever, are equally applied to a palmately compound leaf, and also, 

 and more appropriately, to the case of three or five simple leaves 

 growing on the same node. A pinnately trifoliolate leaf (Fig. 28 G) 

 is readily distinguished by having the two lateral leaflets attached 

 to the petiole at some distance below its apex, and by the joint 

 which is observable at some point between their insertion and the 

 lamina of the terminal leaflet. Such a leaf may even be reduced 

 to a single leaflet ; as in the Orange (Fig. 283) and the primordial 

 leaves of the common Barberry. This is distinguished from a 

 really simple leaf by the joint at the junction of the partial with the 

 general petiole. 



291. The palmate or digitate form is produced when a leaf of the 

 palmately veined sort becomes compound ; in which case the leaflets 

 are necessarily all attached to the apex of the common petiole, as in 

 the Horsechestnut and Buckeye (Fig. 277), and the common Clover 

 (Fig. 304). Such leaves of three, five, or any definite number of 

 leaflets, are termed palmately (or digitately) trifoliolate, Jive-foliolate, 

 &c. A leaf of two leaflets, which rarely occurs, is unijugate (one- 

 paired) or binate. By this nomenclature, the distinction between 

 pinnately and palmately compound leaves is readily kept up, and 

 every important character of a leaf is expressed with brevity and 

 accuracy. 



292. The stalk of a leaflet is called a partial petiole (petiolide) ; 

 and the leaflet thus supported is petiolulate. The partial petioles 

 may bear a set of leaflets, instead of a single one, when the leaf 

 becomes doubly or twice compound. Thus a pinnate leaf again com- 

 pounded in the same way becomes bipinnate (Fig. 282), or if still 

 a third time divided it is tripinnate, &c. In these cases the main 

 divisions or branches of the common petiole are called pinnce, or the 

 pairs jugce. So a trifoliolate leaf twice compound becomes biternate 

 (Fig. 284) ; or thrice, tritemate, &c. "When the primary division 



