354 



MANUAL OP BOTANY 



lies at the back of the bast ; there' is no cambi^■lm left between 

 the bast and wood. 



In the concentric bundle both protoxylem and protophloem 

 can be identified. If the section of the bundle be circular, the 

 protoxylem lies at the centre of the circle {fig. 733). In con- 



Fig. 740. 



Fig, 740. Section of stele of root. After Kny. eit. EDdodermis. pe. Peri- 

 cycle. X. Xyletn bundles, tlie protox,ylem, .-r,, abutting on the pericycle. 

 pli. Phloem bundles alternating witii the bundles of xylem. p. Pith, or 

 coniuuctive tissue of the stele. 



centric gamodesmic bundles there may be several groups of 

 protoxylem, as in some Selaginellas and Ferns (fig. 734). The 

 protophloem arises at one or more points on the outside of the 

 circumferential zone of bast. 



In radially arranged bundles each strand of procambium 

 becomes completely converted into either wood or bast. The 



