THE COMPOUND LEAF 



91 



c to df It is the latter ; that is, it is custom- 

 ary, in speaking of decompound leaves, to use 

 the term leaflet for the last part which is clearly 

 and completely (and more or less uniformly) 

 separated from its neighbors. 



98a. The primary divisions in a palmately decompound leaf (as 

 a b) are not given a distinct name in general botanical literature. 

 The botanist would describe this dieentra leaf (Fig. 87) nearly as fol- 

 lows : Leaf ternately decompound (or sometimes written ternately 

 compound, if the degree of compounding is afterwards specified), the 

 main sections bearing palmately — or even pinnately — divided leaflets, 

 the segments again deeply cut or divided. 



99. The leaf in Fig. 88 (a 

 gum arable tree, a kind of aca- 

 cia) is decompound, and is pin- 

 nate. Each of the numerous 

 entire pieces or parts is called 

 a leaflet, and the six primary 

 parts are pinnas. The leaf is 

 pinnately bi-compound (or twice- 

 compound) . If each of the 

 leaflets was again compound — 

 which is not very rare in 

 plants of this family — the leaf 

 would be said to be tri-com- 

 pound ; the primary parts would stUl be called 

 pinnae, the secondary parts pinnules, and the last 

 complete divisions leaflets. 



100. This acacia leaf has no terminal leaflets. 



Twice-pinnate leaf of 

 acacia. 



