GYMNOSPERMS 



303 



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

 that it li^'es through conditions that would kill deciduous 

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



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- 

 hearing tissue; rd, resin ducts or channels; bsh, handle 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. 



