FORM AND STRUCTURE 



MARGINAL INDENTATIONS. 



A distinction is made between intlentations that are shallow 

 and those that are deep. Of shallow indentations the fol- 

 lowing forms prevail in the leaves of deciduous trees : 

 Serrate, saw-toothed, with sharp teeth which incline toward 



the apex ; distinguished as fnie and coarse. (Fig. 27.) 

 Bi-serrate, doubly serrate, with two sets of teeth one upon 



the other. (Fig. 28.) 



Dentate, toothed with outwardlj' projecting teeth ; distin- 

 guished as fine and coarse. (Fig. 29.) 

 Crenate, scalloped, the teeth broad and rounded. (Fig. 30.) 

 Undulate, when the margin forms a wavy line. (Fig. 31.) 

 Sinuate, deeply wavy. (Fig. 32.) 



Eepand, margin like that of an opened umbrella. (Fig. 33.) 

 Spinose, margin spiny. (Fig. 34.) 



The common forms of deeply indented margins found in 

 the leaves of trees are Lobed and Cleft. 



Lobed, when the indentations extend nearly half-way to the 

 midrib or base, and the segments or sinuses or both may 

 be either rounded or acute. The Oak and the Maple 

 leaves are examples. 

 Cleft, when the sinuses are deep, narrow, and acute. 



509 



