98 



THE LEAF 



with the petiole distinguishes this last case from a simple leaf. In 

 other species of these genera the lateral leaflets also are present. 



184. The leaflets of a compound leaf may be either entire (as in 

 Figs. 124-126), or serrate, or lobed, cleft, parted, etc. ; in fact, may pre- 

 sent all the variations of simple leaves, 

 and the same terms equally apply to 

 them. 



185. When the division is carried 

 so far as to separate what would be 

 one leaflet into tw^o, three, or several, 

 the leaf becomes doubly or twice com- 

 pound, either pinnately or palmately, as 

 the case may be. For example, while 

 the clustered leaves of the Honey 

 Locust are simply pinnate, that is, once 

 pinnate, those on new shoots are bipin- 

 nate, or tioice pimiate, as in Fig. 128. 

 When these leaflets are again divided 

 in the same w^ay, the leaf becomes 

 thrice pinnate, or tripinnate, as in many 

 Acacias. The first divisions are called 

 pinnce ; the others, pinnules ; and the 

 last, or little blades themselves, 

 leaflets. 



186. So the palmate leaf, if again compounded in the same way, 

 becomes twice palmate, or, as we say when the divisions are in threes, 



twice ternate (in Latin form hiternate) ; if a 

 third time compounded, thrice ternate or triter- 

 nate. But if the division goes still further, 

 or if the degree is variable, we simply say 

 that the leaf is decompound ; either palmately 

 or pinnately decompound, as the case may be. 

 Thus, Fig. 129 represents a four times ter- 

 nately compound (in other words a ternately 

 decompound) leaf of a common Meadow Rue. 



187. AVhen the botanist, in describing 

 leaves, wishes to express the number of the 

 leaflets, he may use terms like these : — 



Unifoliolate, for a compound leaf of a single 

 leaflet; from the Latin unum, one, a,ud foliohan, leaflet. 



Bifoliolate, of two leaflets, from the Latin his, twice, and foliolum, 

 leaflet. 



Trifoliolate (or ternate), of three leaflets, as the Clover, and so on. 

 Palmately bifoliolate, trifoliolate, quadrifoliolate, plurifoliolate (of 

 several leaflets), etc. : or else 



128. A twice-pinnate (abruptly) 

 leaf of the Honey Locust. 



12u. 



Ternately decom- 

 pound leaf of 

 Meadow Rue. 



