78 



MANUAL OF BOTANY 



pinnate, or paripinnate, when the main axis of the epipodium 

 is not winged at all, but bears a number of secondary axes which 

 are winged {fig. 94), as in some species of Cassia, the Mastich 

 plant {Pistacia LenUscus), Logwood {Hmmatoxylon cam- 

 pechianum), and Orobus tuberosus ; and it is interruptedly pin- 

 nate (Jig. 150) when the leaflets or secondary winged axes are of 

 different sizes, so that small pinnae are regularly or irregularly 

 intermixed with larger ones, as in the Potato (Solanum tube- 

 rosum) and Silver Weed (Potentilla amserina). AVhen the 

 wing of the main axis is the largest and those of the secondary 



Fig. 150. 



Fig. 152. 



Fig. 151. 



Fig. 150. Interruptedly pinnate leaf of the Potato. Fig. 151. Lyrately 



pinnate leaf. Fig. 152. Bipinnate leaf of a species of Gleditsohia.. 



axes are gradually smaller as they approach the base {fig. 151), 

 it is lyrately pinnate, as in the common Turnip. This leaf and 

 the true lyrate form often run into each other, so that it is by no 

 means uncommon to find both varieties of leaf 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 axes which are 

 arranged on the common one exhibit the characters of an 

 ordinary pinnate leaf, it is said to be bipinnate {fig. 152) ; the 

 leaflets borne by the partial or secondary axes are then com- 

 monly termed pinnules. When the pinnides of a bipinnate leaf 



