20 TREES OP THE NORTHERN UNITED STATES 



pinnate^ 4* when there is an odd leaflet at the end, as in 

 the Ash, W^ and abruptly pinnate Jh AA* when there is 

 no end leaflet. ~<W^ 



Many trees have the leaves twice pinnate; they are either 

 twice odd-pinnate ^^or twice abruptly pinnate. The 



separate blades /TJCrof a compound leaf are J^frff called 

 leaflets. Leaves or leaflets are sessile when $fnffi they 

 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 veinlets join-^^^S^^ 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, 6T&. about as broad 

 as long and rounded. OmZ,^^^ about j}^ twice as long 

 as wide, and regularly "^52^curved. Ellip tical,- <^^^ 

 more than twice as long as wide, and evenly curved. 

 Oblong, ^2^^ two or three times as long as wide, with the 

 sides "^ ^parallel. Linear, ^ elongated oblong, 

 more than three times as ^^ l n g as wide. Acerose. 

 ^^^C^ needle-shaped, like the leaf of the Pine-tree. 



