RAPHANUS SATIVUS 



2-97 



elements of the midrib are oriented more in the adaxial direction and 

 the metaxylem differentiates more in the abaxial direction so that the 

 endarch relationship is attained." 



The Cotyledons. — There are five endarch collateral bundles in 

 the elongated petiole which enter the notched obovate blade. The 



L-2 



Fig. 147. Stages in vascular transition : A, transection of stelar portion of primary root; 

 B, lower hypocotyl, transection of stele showing lateral orientation of metaxylem, and cen- 

 tral parenchyma; C, upper hypocotyl, transection of portion of stele showing laterally 

 oriented metaxylem, and traces of first and second foliage leaves ; D, transection of cotyle- 

 donary bundle ; E, higher in cotyledonary petiole, showing lateral placement of metaxylem : 

 ca, cambium; en, endodermis; L-i and L-i, leaf traces of first and second foliage leaves; 

 mx, metaxylem; pel, pericycle; ph, phloem; pi, pith; px, protoxylem; xy r, secondary 

 xylem. (After Grassley.) 



