THE FIBBO-VASCULAB SY8TJE!M. 



109 



this by one of sieve tissue ; this again by fibrous tissue, and 

 so on. 



137. — A similar but not identical structure is found in the 



Pig. 98.— Part of the cross-section of an old root of Adlantum Morllzianum. h, h. 

 hairs of the root surface ; m,m, bundle sheath (endodermis) ; between h and u. pa- 

 renchyma ; pe, pericambium ; pr, a plate of tracheary tissue, which is boanded on 

 each side by sieve tissue X 225.— After De Bary. 



bundle of the rhizome of Polypodium vulgare. Here the 

 central portion of the stem is made up of scalariform tissue 

 (Fig. 97, the larger, thicker-walled tissue), and this is sur- 

 rounded by a tissue which may be regarded as but partly 



