88 OUTLINES OF PLANT LIFE. 



may develop into fibers, which are quite like the fibers 



h— 



ph — I 



Fig. 77, — Portion of a transverse section of the stem of flax, tn, pith ; k, secondary 

 wood forming a cylinder ; pk, bast ; 6, strands of meclianical tissue (fibers) among 

 the thin-walled cells, the two sorts making up the cortex ; e^, the epidermis. Magni- 

 fied about 25 diam.— After Frank. 



Fig. 78. — ^Transverse section of a bundle pair from the stem of a begonia. The shaded 

 part is the wood strand ; the small irregular cells above are the bast strand ; between 

 them is a zone of growing cells, the stelar cambium, which extends also right and 

 left of the bundle pair. The radius of the section passes through C/'; C, next the 

 center. Magnified 150 diam.— After Haberlandt. 



occurring in the outer part of the stele, 

 are valuable in the textile industries. 



Some of these, also, 



