20 TREES OF THE NORTHERN UNITED STATES 
pinnate, when there is an odd leaflet at the end, as in 
the Ash, NQN™ and abruptly pinnate 4 when there is 
no end leaflet. 
Many trees have the leaves twice pinnate; they are either 
twice odd-pinnate or twice abruptly pinnate., , The 
separate blades of a compound leaf are sasrex called 
leaflets. Leaves or leaflets are sessile when “yt 
have no stems, and petiolate when they have stems. 
When there are several ribs starting together from the 
base of a blade, it is said to be radiate- 
veined or palmate-veined.. When the 
great veins all branch from the 
midrib, the leaf is feather-veined or pinnate-veined. 
If these veins are straight, distinct, and reg- 
ularly placed, the leaf is said to be straight- 
veined. The Chestnut is a good example. 
Leaves having veialets join- ing each other 
like a net are said to be netted-veined. All the trees with 
broad leaves in the northern United States, with one ex- 
ception, have netted-veined foliage. A leaf having its 
veinlets parallel to one another is said to be parallel- 
veined or -nerved. The Ginkgo-tree, the Indian Corn 
and the Calla Lily have parallel-veined leaves. ——« 
The narrow leaves of the cone-bearing trees are | 
also parallel-veined. 
Forms.—Leaves can readily be divided into the three 
following groups with regard to their general outline: 
1. Broadest at the middle. Orbicular, aboutas broad 
as long and rounded. Oval, about Sed twice as long 
as wide, and regularly curved. Elliptical, <=> 
' more than twice as long as wide, and evenly curved. 
Oblong, 27) two or three times as long as wide, with the 
sides parallel. Linear, elongated oblong, 
more than three times as long as wide. Acerose, 
a needle-shaped, like the leaf of the Pine-tree. 
