122 



STKUCTURAL BOTANY. 



[104. 



309. But when the marginal tissue is deficient, the 

 leaf becomes dentate, having sharp teeth pointing out- 

 ward from the center ; serrate, with sharp teeth point- 

 ing forward, like the teeth of a saw ; crenate, with 

 rounded or blunt teeth. The terms denticulate, serru- 

 late, crenulate denote finer indentations of the several 

 kinds ; doubly dentate, etc., denote that the teeth are 

 themselves toothed. 



387 



38T) 



1, Serrate leaf of Chestnut. 382, Doubly serrate leaf of Elm. 383, Dentate leaf of Arrow-wood. 384, 

 Crenate leaf of Catmint. 385, Eepand leaf of Circsea. 386, Undulate leaf of Shingle Oak. 387, Lobed 

 leaf of Chrysanthemum. 



310. The undulate, or wavy edge, is somewhat dif- 

 ferent from the repand, which bends like the margin 

 of an umbrella. If the veins project, and are tipped 

 with spines, the leaf becomes spinous. Irregularly 

 divided margins are said to be erose or jagged, lacini- 

 ate or torn, incised or cut. Often, instead of a defi- 

 ciency, there is a superabundance of marginal tissue, 

 denoted by the term crispate or crisped. 



311. Insertion. Several important terms descrip- 

 tive of the various modes of leaf-insertion must here 





