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. 20S. A Insinuate and multifoliolate leaf of Glo.litscliia or Honey Locust. 

 FIG. 209. Bii.innate leaves of Sensitive Plant, Mimosa pudica, with approximate 

 pinnae. 



