114 



BOTANY. 



Lying by the side of the tracheary tissue (on its outer side as 

 it is placed in the stem) is a mass of sieve tissue, composed of 

 latticed cells {v, v, Pig. 103). Surrounding the whole is a 

 thick mass of fibrous tissue ■ composed of elongated, thick- 

 walled cells (the shaded ones in the figure). 



143. — The fibre-vascular bundle of the flowering-stalk of 

 Acorus calamus bears a close resemblance to that of Indian" 

 corn. Like that, it has a central tracheary portion {g, Fig. 

 103), which has lying exterior to it a mass of sieve tissue {w. 



Fig. 103). On the inner 

 side there is a large in- 

 tercellular canal, evi- 

 dently holding the same 

 relation to the other 

 tissues that the emaller 

 canal does in the bundle 

 of Indian corn. The 

 exterior of the bundle 

 is here also made np of 

 a thick mass of fibrous 

 tissue. 



144. — In the fibro- 

 vascular bundle of the 

 adventitious roots of 

 Acorus calamus the ar- 

 rangement of the tis- 

 sues is very different 

 from that described 

 above. Here there are 

 many radially placed 

 plates of tracheary tissue {pp, Fig. 104), which alternate 

 with thick masses of sieve tissue {ph, Fig. 104). Between 

 these alternating tissues, and within the circle formed by 

 them, there is a mass of parenchymatous tissue. The 

 whole bundle is separated from the large-celled parenchyma 

 of the root by a well-marked bundle sheath (s, Fig. 104) ; 

 the latter is bounded interiorly by a layer of active thin- 

 walled cells — the pericambium — from which new roots 

 •originate. In the older root, the central cell mass (which, 



Fig. 103.— Transverse section of a portion of 

 the general peduncle of Acoi'us calamus, e, epi- 

 dermis ; &, small fibro-vascular bundle ; in the 

 large bundle w is the sieve tiacue, g the traclie- 

 ary tissue, I an intercellular canal ; the periphery 

 of the bundle is composed of thick-walled fibrous 

 tissue (figured dark). X 145.— Alter De Bary. 



