110 



BOTANY. 



differentiateJ, being composed of parenchyma and poorly 

 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. !N"ext 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 {ii, Fig. 

 98). 



139. — In the 

 stem of Equise- 



Kg. 99.— Transverse section of a flbro-vascular bundle of , 7 ^ •(• 



^QU^eiumpalusfn. r, i, ringed vesseln on the border of a tWHl pCllUStTe ID 



large intercellular canal; », sieve tissue; g,g, groups of ■ . oqett- aa 



annular and reticuliited vessels; w, the so-called general -^^ iiuu fcu tjaci^ d.& 



bundle sheath, which surrounds all the bundles ; i, i, axial ,•„ j->,„ •frvTorTr>iTirr 



air canals; x , x , fragments of the ruptured cells. X 145. '" ^"*^ ioregomg 



-After De Bary. cascs to mark the 



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 EquUetum limosum, however, there is a bundle sheath about 

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

 the limits of tlie bundle. 



