34 



THE INDIANA WEED BOOK. 



narrower portion by which it is joined to the stem or branch is the 

 stalk or petiole. Leaves which have no stalks, the blades being 

 joined by one end directly to the stem, are sessile. In position on 

 the stem they are opposite or in. pairs as in the corn cockle; alter- 

 nate or scattered singly along the stem, one above another on op- 

 posite sides, as in the mullen, or whorled if three or more come off 

 in a circle at the same level. 



In shape the leaves of weeds vary greatly, some of the forms 

 being ovate or egg-shaped; lanceolate, narrower and more elongate 

 than ovate and tapering to a point like a lance ; cordate or heart- 

 shaped; reniform. or kidney-shaped, that is heart-shaped at base 

 but broader than long and not pointed ; hastate or halberd-shaped, 



Fig. 8. Showing forms of leaves: o, ovate; 6, cordate or heart-shaped; c, sagittate or arrow-shaped' 

 d, hastate; e, reniform or kidney-shaped; /, rounded or orbicular; g t spatulate or spoon-shaped; A, oblong ana 

 obtuse; i, linear; j, lanceolate; k, 3-parted or 3-divided; I, with apex notched or emarginate. (After Gray.) 



with the lobes at base pointed outward ; oblong or narrowly ovate 

 and usually dull at tip : spatulate or spoon-shaped, that is broader 

 toward the apex; orbicular or rounded, and linear or long and nar- 

 row as those of the corn cockle. The linear leaves of endogens like 

 grasses, sedges and lilies have only long straight parallel veins, 

 while those of exogens have netted veins which interlace and run 

 together so as to form a network. (Fig. 15 b, d.) 



The edge or border of the leaf is either entire or variously 

 toothed, lobed or deeply parted. When the lobes are divided clear 

 to the midrib or the main vein at center, the leaf is said to be 

 compound, otherwise it is simple. Each of the leaflets or divisions 

 of a compound leaf may be divided into segments and these again 



