CH. IX] HISTOLOGY. 125 



larised brown-coloured cells, which in longitudinal section 

 are seen to be only slightly elongated ; they do not 

 contain starch. 



FIG. 54. 



TRANSVERSE SECTION OF A BUNDLE IN THE RHIZOME OP Pteris. 



e, endodermis, outside which is parenchymatous tissue p. 

 p.c, pericycle. p.phl, protophloem. 



s.t, sieve-tube. sc.v, scalariform vessel. 



Inside the bundle-sheath is an irregular layer of 

 colourless softer cells, which differ from those of the 

 bundle -sheath in containing starch : these form the peri- 

 cycle. The rest of the bundle is made up of the same 

 two main classes of tissue as those seen in the sunflower 

 and oak, namely, xylem and phloem : the centre of 

 each bundle is xylem and is surrounded, not completely 

 but on two opposite flanks, by the phloem. There is 

 no cambium. 



What was said in an earlier chapter as to the general 

 characteristics of vascular tissue, holds good in the case 

 of the fern. 



