110 



BOTANY. 



differentiated, being composed of parenchyma and poorlv 

 developed sieve tubes (s, Fig. 97). The whole bundle is sur- 

 rounded, as in Pteris aquilina, by a bundle sheath (u, Fig. 

 97). In the outer part of the mass of scalariform tissue are 

 a few narrow spiral vessels (sp, sp, Fig. 97), but they are 

 not sufficiently numerous to constitute a ring or layer. 

 138. In the root of Adiantum Moritzianum the bundle 



consists of a cen- 

 tral plate of tra- 

 cheary tissue ( pr, 

 Fig. 98), with a 

 mass of sieve 

 tissue on each 

 side of but not 

 quite enveloping 

 it. Next outside 

 of this is a layer 

 of active paren- 

 chyma, the peri- 

 cambium (pc, 

 Fig. 98), and sur- 

 rounding the 

 whole is a poorly 

 developed bundle 

 sheath (., Fig. 

 98). 



139. In the 

 stem of Equisc- 



Fig. 99. Transverse section < f a fibre-vascular bundle of , 7 



Kqulsffjm paluslrf. r, t, ringed vessel* on the border of a tuill palUStre it 



large intercellular canal ; , sieve tissue ; ff, q. groups of 



annular and reticiihted vessels; M. the so-called general 1* DOI BO easy as 



bundle sheath, which surrounds all the bundks ; t, i, axial ;,, J-), P fnrpo-ninr- 



air canals; x , x , fragments of the ruptured cells, x 145. m tlie lOregOing 



-After De Bary. cages to mark t lie 



limits of the bundles, which are arranged in a circle about 

 the axis.* On the axial side of each bundle there are at 

 first a few spiral and annular vessels, most of which, 

 along with a considerable amount of parenchyma, are 



* In Equisetum limosum, however, there is a bundle sheath about, 

 each bundle, consequently there is in that species no difficulty as to 

 the limits of the bundle. 



