CH. V, 10] SUMMARY OF PLANT TISSUES 



263 





FIG. 182. Vertical section through a 

 generalized plant, to show the typical ar- 

 rangement of the tissue systems. 



Outside is the dermal system (double 

 lined), formed by the dermatogen region in 

 the bud, and providing the protective epi- 

 dermis on leaf and stem, and the hair layer 

 on the young root. Next is the cortical 

 system (crosses), formed by the periblem 

 region of the bud, and providing the chloren- 

 chyma of leaf and young stem, with cortex 

 of bark and young root. Next is the central 

 cylinder, or stele, formed by the plerome 

 region of the bud, and providing the vascular 

 bundles, with the pith (coarse dotted). 

 The bundles include food-conducting phloem 

 (cross lined), and water-conducting xylem 

 (diagonally lined), with cambium (fine dotted) 

 between them. The growing points of roots 

 and stems (also fine dotted) with the cam- 

 bium which unites them constitute the 

 growth system. 



