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 wnegually pinnate when it is terminated by an 
odd leaflet or by atendril. Ex. rose, locust, pea. In the latter 
case the leaf is called czrrhose. 
3. An interruptedly pinnate leaf has the leaflets alternately 
small 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 pimne (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 bipinnate leaf (twice pinnate), is formed when the leaf- 
lets of a pinnate leaf themselves become pinnate. Ex. Fuma- 
ria officinalis. 
6. A tripinnate leaf (thrice 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 al] 
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 formed when the leaflets of the ternate 
leaf become themselves ternate, as in Fumaria lutea. 
8. A triternate leaf is formed when 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, 
é&c., already mentioned ; 
