THE GROWTH OF ROOTS AND STEMS. 



167 



(bast) lying partly between the two larger vessels ; and the more or 

 less complete sheath of fibres around the bundle. The larger wood- 

 vessels are pitted ; the smaller ones have rings or spiral thickenings. 

 The bast, which stands out distinctly in sections treated with 

 aniline chloride (its walls being of cellulose and therefore not stained), 



INTERFASC. CAMBIUM -, 

 MED. RAY 

 TISSU 



.-. ' OOD BITTED 

 I, g? FIBRES VESSELS 



BAST / ENDODERMI! 

 / \ HARD BAST ,' 



SIEVE TUBES 



Fig. 57. Transverse (upper) Longitudinal (lower) Sections of Part of a 

 Sunflower Stem. 



consists of sieve-tubes alternating regularly with narrow cells (com- 

 panion-cells), but the tubes are narrow and rather difficult to make 

 out clearly. Compare the relative amounts of sclerenchyma and of 

 vascular tissue (wood and bast) in bundles in different parts of the 

 section. It is easy to see that the hard tissue (stained yellow with 



