48 PRACTICAL BOTANY. 



97. The Sueface of the blade of a leaf is said to be 

 undulate, or wavy, if bent tip and down ; crisp, wlien bent 

 irregularly up and down ; rugose, wrinkled ; plicate, or 

 folded, gathered into longitudinal folds ; nervose, or nerv- 

 ed, with strong vascular bundles, nerves, or ribs y veined, 

 having thin and slender vascular bundles, especially 

 branching ones, veins. "We distinguish nettedrveined (PI. 

 n., 12) and jparallelrveined leaves (PI. II., 10), and other 

 sorts of venation, which will be considered presently in 

 connection with certain divisions of the margin. 



98. The division of the margin of leaves with refer- 

 ence to the framework of their surface. 



Leaves are, as regards the principal bundles of their 

 woody fibres, either feather-veined (jnnnately-veined) or 

 radiate-reined (the same as palmafely-veined). 



The first-named sort has only one longitudinal rib or 

 nerve, extending from the top of the petiole to the apex 

 of the leaf, and this rib, also called the midrih, sends out 

 branches, or veins, which are divided into branchlets or 

 veinlets. Sometimes the two lowest branches of the mid- 

 rib arc very strong and long, and the leaf is then called 

 triple^rihhed or triple-nerved. 



The other sort has three to five or more ribs or nerves, 

 instead of a single one ; hence we distinguish' three-rihhed 

 (triple-nerved), five^iUbed, seven-rihhed, etc., lea/oes. 



Now, according to these two modes of venation, we 

 distinguish two modes of division into segments, calling 

 some le&ves pimiatelj/- and othevsjpahnatdy-cl^, parted, 

 or divided, (See PI. II., 3-6.) A few modifications of 

 pi/mrntehj-deft orpaHed leaves are designated by particular 

 terms. Pectinate we call pinnately-parted leaves, with 

 very close and narrow divisions, resembling the teeth of a 

 comb ; lyrate, <yr lyre-shaped, those with the segments de- 



