90 THE LEAF. 



2G Acerose (needle-shaped),.Kvhen there is little or no distinc- 

 tion of lamina, petiole, or veins, as in the leaves of the pine.j 



§ 5. MARGIN. 



235. The margin of the leaf is also modifi2d cliiefly by the 

 same canses Avhich affect the form. It is s^id to be 



1. £n/iVc,.^-hen even-edged. This may result from the full development of the 

 tissue, or from a vein running parallel ^\ith the margin. Ex. lilac, lily. 



2. Dentate (toothed), 'the tissue incomplete, having teeth -ndth concave edges, 

 pointing outwards from the centre. Ex. hawkweed. If the teeth are very fine, 

 the margin is said to be denticulate. If the teeth are themselves toothed, it is 

 doubly dentate. -^ 



. 3. &r/a<c, paving shai-j) teeth pointing fonvard like the teeth of a saw Ex 

 Eosa. If the sciTatiu-es are very small, it is sarulate. If they are themselves 

 serrate, it is doubly serrate. ) 



4. Oenafe,Aiotched with rounded or convex teeth, as in Glechoma. If such 

 notches are very small, it is cremdate. ' 



5. Erase (gnawed)/ having the mai'gin ii-regularly tootlied, or jagged, as if 

 bitten by animals. . 



6. Undidate ( wavy ),^ the margin rising and falling IQie waves. Ex. Amaranthus. 



7. Spinous, when the veins project far beyond the tissue in shai-p spines, as in 

 tlie thistle. Such leaves are said to be armed, and the opposite coiTCsponding 

 term is unarmed. 



8. Incised (cut), margin divided by deep incisions. 



9. Laciniate (torn), divided by deep and in-egular gashes. 



10. Crisped, margin much expanded and curled by a superabundance of tissue, 

 as in the mallows. _ 



11. iJepanrf, having the margin slightly concave between the projecting veins. 

 Ex. Solanum nigrum. 



. §6. APEX. 



236. In regard to the termination of a leaf at its apex, it is 

 said to be 



1. ^cM<«, when it ends with an acute angle. 



2. Obtuse, when it ends with a segment of a circle. 



3. Acuminate, ending with a long, tapeiing point. 



4. Emarginate, ha'v'ing a small notch at the end. 



5. Retuse, terminating with a round end, having the centre depressed. 



6. Mucronate, abruptly terminated by a short, hard, bristly point, &c. 



§ 7. SURFACE. 



237. The following terms are employed in descriptive botany, 

 chiefly to denote the modifications of the sm-face (epidermis) 



