THE LEAVES. 



19 



Wrinkled, when the veins are tighter than the substance be- 

 tween them, so that the latter becomes puckered. 



Plaited (Fig. 69.), when the leaf is folded, so as to present 

 alternately projecting and retiring angles. 



Curled, when the margin is greatly more expanded than the 

 disk, and the leaf thus becomes folded or curled. 



Naked, destitute of all kinds of hairiness. 



With respect to substance, Simple Leaves are 



Membranous, when very thin and easily torn. 



Leathery, when thin but very tough. 



Fleshy, when more or less thick and juicy. 



Cartilaginous, when more or less thick and tough. 



Flat, opposed to the following : 



Cylindrical or round; Semi-cylindrical, flat on one side, and 

 round on the other. 



Compressed, when thick and flattened laterally. 



Depressed, flattened vertically. 



Channelled (Fig. 70.), having a longitudinal groove. 



ee/erf(Fig.7l.),havingalongitudinal prominence or ridge on 

 the back. 



Sword-shaped, perpendicular, two-edged, and slightly convex 

 on both surfaces. 



Awl-shaped (Fig. 72.), long, cylindrical at the base, and 

 tapering to a point. 



Hair-shaped or Bristle-shaped, the same, but more slender. 



Hollow or Tubular, more or less cylindrical and empty. 



Jointed or articulate, divided into cavities by transverse par- 

 titions. 



Two-edged, Three-sided or Three-edged, Four-sided, &c. 



With respect to duration, Leaves are 

 Caducous, when they fall soon after their development. 

 Deciduous, when they fall before the next spring. 

 Marcescent, when they wither before falling. 

 Persistent, Permanent, or Evergreen, when they remain longer 

 than a year. 



Compound Leaves are named as follows : 

 Compound Leaves are such as present a greater or less number 

 of distinct parts, connected by a common stalk. The distinct 



