ORGANS OF NCTRITION. 



169 



as in some species Cassia, and Orohus tuherosus ; it is interruptedly 

 pinnate {fiy. 336) when the leaflets are of different sizes, so that 

 small pinnffi are regularly or irregularly intermixed with larger 

 ones, as in the Potato and Silver Weed {Potentilla anserina). When 

 the terminal leaflet of a pinnate leaf is largest, and the rest 

 gradually smaller as they approach the base (Jig. 337), it is 

 lyratelij pinnate ; this leaf and the true lyrate are frequently 

 confounded together by botanists, and the two forms frequently 

 run into each other, so that it is by no means uncommon to find 

 both on the same plant, as in the common Turnip and Yellow 

 Rocket. 



When the leaflets of a pinnate leaf become themselves pinnate, 

 or in other words when the partial petioles which are arranged 

 on the common petiole exhibit the characters of an ordi- 

 nary pinnate leaf, it is said to be bipinnute {fig. 338 and 366), 



Fig. 338. 



. 339. 



Fig. 338. Bipinnate leaf of a species of Gleditschia. Fig. 399. A tii- 



pinnate leaf. 



