20 ELEMENTS OF BOTANY. 



etc, Wlion flic inoisionH arc carriod Htill dcopor, tlio frrm parted is UHcd ; 

 ami when tlioy cxteml to the mid- vein or biiHc of the bliulo, tho leaf is naid 

 to be divided. 



In general outline leaves present a miiltiiilicity of forms, Avhich are, 

 however, siitlicicntly characterized in non-technical language. Such terms 

 as linear, hino'olnle, oblon(j, elliplical, oval, ovoid, and orbicular are often 

 employed, and recpiire no exi)liination. Ohlanci'olalc signifies a grnerid 

 lance-shape, but somewhat widened toward the apex, like a lance Avith its 

 point turned downward ; obomte, an ovate form also with its wider por- 

 tion toward tho apex ; spafidntc, like a spatula ; cnnecUc, wedge-shaped, ta- 

 liering from above downward. 



Then, too, the base and apex present a variety of forms. The base 

 may be eordalr, or heart-shaped, reni/orm or kidney-shaped, aiiriciihif 

 or eared, i<(i(jil/ul<! or arrow-shaped, hmlale or halberd-shai^ed, jfjcZ/w/tf or 

 shield-shaped. 



The ajiex may be acuminate or taper-pointed ; acute when ending with 

 an uouu! angle and not tapering ; obtuse, blunt ; truncate, appearing as if 

 cut off; rctuse, slightly notched at the extremity ; rmarginate, more deeply 

 notched or indented ; olwordate, inversely heart-shaped ; cuxpidate, armed 

 with a small cusp or tooth ; m ucrovatc, armed with a very small sharp 

 point ; or aridate, with a bi istle-like point. 



Thus far we have considered the leaf in its simplest form — that is, when 

 consisting of a single blade, however deeply it may be cut or divided. 

 All such leaves are termed simple (Fig. 29), in contradistinction witli 

 compound leaves (Fig. 30), which are made \\\) of two or more, often 

 manj' bLides, supi)orted by a common petiole. Yet this distinction of 

 leaves iiito simple and compound is, to some extent, arbitrary, for in leaves 

 which are jmrted — that is, divided to the base or mid-vein — the lobes be- 

 (!ome as essentially separate blades as if they were supported upon sepa- 

 rate petioles : still, such leaves are commonly considei-ed simple. Some 

 writers simplify the matter by drawing the line at a. aculation with tlie 

 petiole, considering those only compound which ai*e so articulated and all 

 others simple. ]>y articulation is meant the joint at which the leaf sepa- 

 rates when it falls from the stem. But even this division is not com- 

 pletely satisfactory, for there are leaves — for example, tho lemon — con- 

 sisting of a single entire blade which is articulated with its petiole, and 

 hence would under this definition have to be considered a compound leaf. 



A compound leaf, then, is made up of two or more blades, termed leaf- 

 lets (Fig. 30), borne upon a common petiole, with which they may or may 

 not be articulated. 



Compound leaves are of two principal forms, the pinnate, in which 

 the leaflets are arranged like the pinnate veins of a simple feather-veined 

 leaf, and the palmate, in which tliey are arranged palmately. 



Pinnately compoimd leaves are equally pinnate when they have 



