BETA VULGARIS 



171 



fascicular cambium become inactive and differentiate as vascular 

 tissue or parenchyma; but the continuity of the extrafascicular 

 cambial ring is reestablished by the formation of newr sectors of 



Fig. 134. Transection of portion of stem showing development of secondary and tertiary- 

 tissues : CO, cortex ; col, coUenchyma ; cu, cuticle ; en, endodermis ; e^, epidermis ; jas ca, 

 fascicular cambium ; int ca, interfascicular cambium ; pel ca, pericyclic cambium ; pi fib, 

 pericyclic fiber; fh z, secondary phloem; ph 3, tertiary phloem; pi, pith; xy i, primary 

 xylem ; xy i, secondary xylem ; atj 3, tertiary xylem. 



cambium from the pericyclic cells located on the outer face of the 

 last-formed phloem. This type of axial thickening continues as 

 long as the stem lives. 



The Course of the Bundles in the STEM^-^^^^'-'^FhFphyllotaxy of 

 the floral axis is usuall^L^lternate with a % divergence, although 



