160 COMPENDIUM OF GENERAL BOTANY. 



with axillary buds, the remaining two or four are stipules. 1 (Func- 

 tion of grass-ligules ?) 



The petiole is the stem-like support of the leaf-blade. If the 

 petiole is absent, the leaf is said to be "sessile." Sometimes a leaf- 

 portion resembling the petiole alone is developed, usually as a ten- 

 dril. In some plants the petiole is flattened, as in the phyllodes of 

 Acacia ; these are not to be confounded with the phyllocladea of 

 Ruscus, for example, which are leaf-like stems and bear leaves 

 themselves. In cross-section the petiole usually presents the appear- 

 ance of a horseshoe; such structural arrangement serves to increase 

 the mechanical support. 



The Hade terminates the petiole of the sheath as the true leaf-ex- 

 pansion. In the assimilating foliage-leaves it is strongly developed, 

 also in the petals of the corolla ; the calyx is usually a modification 

 of the sheath-portion. It is not intended to enter into an extended 

 discussion of the morphology of the blade, though some such 

 knowledge is necessary in order to understand the various modifica- 

 tions of the form of the blade. 



Usually the blade is recognized as the leaf-surface or simply the 

 leaf. It may be linear (about four times as long as broad), oval 

 (about twice as long as broad), or elliptical (distinguished from the 

 oval by the angles at apex and base). In regard to the base the 

 leaf may be narrowed, rounded, cordate, auriculate or eared when 

 the inner side of the lobe is rounded, hastate or halberd-shaped when 

 the base is cut straight across, sagittate when the lobes are directed 

 outward. The tip or apex of the leaf may be rounded, blunt, 

 obtuse, mucronate, acuminate, truncate when it seems cut across, 

 emarginate when there is a depression at the apex, obcordate when 

 the depression is deep. 



If the leaf-margin is not divided or cut, it is said to be entire; 

 it is toothed when the projections at the margin point outward, 

 serrate when the projections slant forward, crenate when the pro- 

 jections are rounded and the depressions pointed, sinuate when 

 projections and depressions are both rounded. Usually the leaf- 

 surface is even, sometimes repand, undulate, or wavy, especially 

 toward the margin ; or it may be variously folded, either longi- 

 tudinally, transversely, or radially. 



WARMING (POTTER), Handbook of Systematic Botany, 1895. 



