92 THE LEAF. 



(which is usually supported on a distinct stalk), is articulated 

 (articula, a joint), with the main petiole, and separates from ^it 

 in decay. 



240. From the feather veined arrangement may result the 

 following forms of compound leaves : 



1. Pinnate (winged), where the petiole (midvein) bears a row 

 of leaflets on each side, generally equal in number and oppo- 

 site, as in the Acacia. 



2. A pinnate leaf is said to be equally pinnate where the 

 petiole is terminated by neither leaflet nor tendril, as the Cassia 

 Marilandica, and unequally ^nnnate when it is terminated by an 

 odd leaflet or by a tendril. Ex. rose, locust, pea. In the latter 

 case the leaf is called cinhose. 



3. An interruptedly pinnate leaf has the leaflets alternately 

 smaU and large, as in the potato, avens. 



4. A pinnate leaf sometimes consists of as many as twenty or 

 thirty pairs of leaflets, as in the Astragalus. Sometimes the 

 number of leaflets is but three, and the leaf becomes ternate or 

 trifoliate, as in the ash ; and, finally, it is sometimes, by the non- 

 development of the pinna (pairs) reduced to a single terminal 

 leaflet, as in the lemon. Such a leaf is known to be compound 

 by the articulation of the leaflet to the petiole. 



5. A bipinnatc leaf (twice pinnate), is formed when the leaf- 

 lets of a pinnate leaf themselves become pinnate. Ex. Fuma- 

 ria officinalis. 



6. A tripinnate leaf (tlirice pinnate), is formed when the leaf- 

 lets of a bipinnate leaf become pinnate, Ex. Aralia spinosa. In 

 the leaf of the honey-locust (Gleditschia), we sometimes find all 

 these three degrees of division, namely, the pinnate, bipinnate, 

 and tripinnate, curiously combined, illustrating the gradual tran- 

 sition of the simple to the most compound leaf 



7. A biternate leaf is fonned when the leaflets of the temate 

 leaf become themselves ternate, as in Famaria lutea. 



8. A triternate leaf is formed wdien the leaflets of a biternate 

 leaf become again ternate. Ex. Aquilegia. 



241. The following forms of compound leaves may result 

 from the division of a radiate-veined leaf; the ternate, biternate, 

 &c., already mentioned ; 



