152 PRACTICAL BOTANY 



serve especially that the parenchyma, lying centrally to 

 the phloem, has begun to divide repeatedly by tangential 

 walls : in fact, four cambium bands are thus formed, 

 from which is derived the secondary thickening of 

 the root. 



IV. Cut transverse sections of an old root of the 

 Scarlet-Runner, taking care here also to avoid the base 

 of the hypocotyledonary stem, and treat as before. 

 Observe 



1. Centrally a parenchymatous pith. 



2. The primary xylem groups, usually four in 

 number, retain their original position, relatively to the 

 pith. 



3. Four large wedges of secondary xylem have 

 originated internally from the four cambium zones. 

 These are separated from one another laterally by 



4. Four broad parenchymatous rays, which lie 

 on the same radii as the primary xylem. Outside 

 the xylem is 



5. The cambium, having similar characters to that 

 of the stem, and giving rise peripherally to 



6. Secondary phloem. Note if possible 



7. The four groups of primary phloem now 

 separated from the primary xylem, but still on radii 

 alternating with the latter. The section is bounded 

 by- 



8. A narrow band of cork with a cork-cambium at 

 its inner limit : this originates from the pericycle, 

 and this point should be ascertained by cutting sections 

 successively at older points. It is to be noted that the 

 endodermis, cortex, and piliferous layer, are absent in 

 these sections, these being thrown off on the formation 



