HISTOLOGY OF ANGIOSPERM STEM, ROOT, ETC. 



99 



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rupted here and there by the underlying thin-walled 

 parenchyma, the epider- 

 mis showing at some of 

 these places a stoma; o 

 the outermost portion 

 of the phloem (proto- 

 phloem ) is frequently LL 

 crushed and disorgan- 

 ised ; the sieve - tubes 

 and companion-cells are 

 arranged with great 

 regularity ; the inner- 

 most portion of the 

 xylem (protoxylem) is 

 usually represented by 

 a water- containing cav- 

 ity (formed by expan- 

 sion and tearing apart 

 of the protoxylem dur- 

 ing growth of the stem), 

 to the inside of which 

 isolated ring-fibres may 

 be seen adhering. 



108. L. S. Maize 

 Stem (Figs. 29, 30). 

 In longitudinal sections 

 note the (1) epidermis 

 (oblong cells), with 

 cuticle ; (2) scleren- 

 chyma (long tapering CD 

 lignified fibres) ; (3) 

 parenchyma (poly- 

 gonal thin- walled cells) ; 

 and (4) the vascular 

 bundles, each sur- 

 rounded by its fibrous 

 sheath. Examine seve- 

 ral bundles, if necessary, 

 to make out (5) the large pitted vessels, (6) the small 



