BOTANICAL CHARACTERS 



77 



67. The Stem and Its Functions .—The stem grows upward chap. 

 and bears the leaves and inflorescences (Fig. 1 2). It is built up IV - 

 of a series of lengths or intemodes connected by joints or 



Fig. 21. — Part of a radial longitudinal section of stem of maize, showing 

 one of the vascular bundles. A and G, parenchyma of the ground tissue; B and 

 F, sclerenchyma ; C, phloem ; D, pitted vessels of the xylem ; E, spiral and 

 annular vessels. (From Cavers' Practical Botany, W. B. Clive.) 



nodes. In many grasses it is hollow, but in the maize plant 

 it is filled with, pith, which consists largely of cellulose. The 

 hard outer portion or stem-wall contains numbers of fibres 

 called vascular bundles (Fig. 19), through the woody part 



Fig. 22. — Part of a tangential longitudinal section of stem of maize, show- 

 ing one of the vascular bundles. A and E, parenchyma (ground tissue) ; B and 

 D, sclerenchyma; C, xylem — note the large pitted vessel on either side, and the 

 small pitted vessels in the middle. (From Cavers' Practical Botany, W. B. 

 Clive.) 



[xylem) of which the solution of water and food-material ab- 

 sorbed by the roots travels upward to the leaves. As in other 

 grasses the stem-wall is well supplied with silica, which aids 



