LECT. X.] COMPOUND LEAVES. 523 



from one leaflet to another, down the common 

 petiole; but this is the description of the pin- 

 natifid leaf; for the real decurrently pinnate is a 

 modification of the jointedly pinnate, each joint 

 consisting of one pair of pinnae supported on a 

 winged petiole (see fig. 91, page 521, a. a. a.). In 

 some instances the leaflets, instead of being ar- 

 ranged in the same plane on each side of the com- 

 mon petiole, are placed around it; and the leaf 

 is consequently termed verticillato-pinnatum. 



2. The second division of compounded leaves, 

 the doubly compound, comprehends those leaves in 

 which the common petiole is divided into, or sup- 

 ports secondary petioles. 



When near the apex of the common petiole, 

 there is a single pair of secondary petioles, each 

 of which supports a pair of opposite leaflets, as in 

 Mimosa unguis cati, the leaf is termed twice 

 paired (bigeminatum, seu biconjugatumj , Q2: it is 



92 



