152 



PRACTICAL COURSE IN BOTANY 



FIG. 190. Narrow leaves 

 in crowded vertical rows. 



bane and bitterweed (Helenium 

 tenuifolium) , illustrate this relation. 



On the other hand, when the leaves 

 are large and rounded in outline, as 

 those of , the sunflower, hollyhock, and 

 catalpa, they are usually separated 

 by longer internodes, or their blades 

 are cut and incised so that the sun- 

 light easily strikes through to the 

 lower ones. 



1 70 . Other external characteristics 

 to be observed in leaves are : 

 whether round, oval, heart-shaped, 



(1) General Outline 

 etc. (Figs. 191-197). 



(2) Margins: whether unbroken (entire), or variously 

 toothed and indented. (Figs. 198-202.) 



195 



FIGS. 191-197. Shapes of leaves : 191, lanceolate ; 192, spatulate ; 193, oval ; 

 194,obovate; 195, kidney-shaped ; 196, deltoid; 197,lyrate. (191-195 after GRAY.) 



(3) Texture: whether thick, thin, soft, hard, fleshy, 

 leathery, brittle. 



(4) Surface: smooth, shining, dull, wrinkled, hairy, or 

 otherwise roughened. 



