102 



STRUCTURAL BOTANY. 



leaflet, and interruptedly pinnate when the leaflets are alter- 

 nately large and small (358). 



303. The number of leaflets in the pinnate leaf ~\ aries from 

 thirty pairs and upward (as in some Acacias), down to three, 

 when the leaf is said to be ternate or trifoliate ; or two, becom- 

 ing binate ; or finally even to one leaflet in the Lemon. Such a 

 loaf is theoretically compound, on account of the leaflet (blade) 

 being articulated to the petiole. 



und leaves. 359, Clematis. 360, Erigenia bulbosa, 361. Acacia. 362. Honey-locust 



304. A bipinnate leaf (twice pinnate) is formed when the 

 rachis bears pinnae, or secondary pinnate leaves, instead of leaf- 

 lets (361), and tripinnate (thrice pinnate) when pinnre take the 

 places of the leaflets of a bipinnate leaf (360). When the divi- 

 sion is still more complicated, the leaf is decompound. Different 

 degrees of division often exist in different parts of the same leaf, 

 illustrating the gradual transition of leaves from simple to com- 

 pound in all stages. The leaves of the Honey-locust and Coffee- 

 tree (Gymnocladus) often afford curious and instructive exam- 

 ples (362). 



305. A biternate leaf is formed when the leaflets of a ternate 

 leaf give place themselves to ternate leaves (359), and triternate 

 when the leaflets of a biternate leaf again give place to ternate 

 leaves. 



306. Palmately compound. The palmate venation Lae 



