GYMNOSPERMS 



303 



occur very slowly. It conserves its water supply in such a way 

 that it lives through conditions that would kill deciduous 

 leaves. The leaf surface is greatly reduced. The leaf seems to 



,ep 



rd. 



FIG. 249. Part of a cross section of a pine needle leaf 



ep, the epidermis, upon which is a layer of cuticle ; scl, a layer of heavy- walled cells, 

 or sclerenchyma ; st, stomata with deeply placed guard cells; chl, chlorophyll- 

 bearing tissue ; rd, resin ducts or channels ; bsh, bundle sheath which incloses 

 - two vascular bundles, one shown at vb 



have secured protective form and covering at the expense of 

 abundant chlorophyll exposure. It can perhaps begin to work 

 earlier in the season and work later than can deciduous leaves. 



