THEIR STRUCTURE AND FORMS. 



103 



simple leaves. As leaflets may be toothed, lobed, or parted, so 

 what answers to a single leaflet may appear as leaflets of a second, 

 or again of a third, or even of a fourth order. Decompound is a 

 good general name for all more than once compounded leaves ; 



but the name has been applied rather to irregularly many-times 

 parted or dissected leaves (such as those of Dicentra), or to 

 those more than thrice compounded. Of regularly twice or 

 thrice compound leaves, the commonest are the 



Bipinnate or Twice Pinnate, of ordinary 

 occurrence in the Mimoseous and Caesalpi- 

 neous, but not in the Papilionaceous, Legu- 

 minosse. Fig. 208 represents a bipinnate leaf 

 of the Honey Locust (Gleditschia) , with the 

 variation (common with that tree) that some 

 of the partial petioles, in this figure only the 

 lowest, bears a single leaflet, while the others 

 are extended into secondary rhachises fur- 

 nished with numer- 

 ous leaflets, mostly 

 in the abruptly pin- 

 nate style. On the 

 same tree, the earlier 

 leaves, which are 

 clustered on short 

 spurs, are simply 

 pinnate. The large 

 leaves of Gymnocladus are similarly and abruptly bipinnate, 



FIG. 208. A bipinnate and multifoliolate leaf of Gleditschia or Honey Locust. 

 FIG. 200. Bipinnate leaves of Sensitive Plant, Mimosa pudica, with approximate 

 pinnse. 



