64 ELEMENTS OP BOTANY. 



another stem of the same kind or a closely similar kind of 

 plant, the two may grow together to form a single stem or 

 branch. This process is called grafting, and is much resorted 

 to in order to secure apples, pears, etc., of any desired kind. 

 A twig from a tree of the chosen variety is grafted on to any 

 kind of tree of the same species (or sometimes a related species), 

 and the resulting stems will bear the wished-for kind of fruit. 



Stem of Monocotyledonous Plants. 



87. General Structure. — Cut across a corn-stalk and examine the cut 

 surface with the magnifying glass. Note the firm rind, composed of the 

 epidermis and underlying tissue, the large mass of pith composing the 

 main hulk of the stem, and the fibro-vascular bundles, or groups of wood- 

 cells, hast-oells, and vessels. 



In what part of the stem are these bundles most abundant ? 



Split a portion of the stem lengthwise and notice whether the bundles 

 seem to run straight up and down its length. Every fibro-vascular bun- 

 dle of the stem passes outward through some node in order to connect 

 with some fibro-vascular bundle of a leaf. This fact being known to the 

 student would lead him to expect to find the bundles bending out of a 

 vertical position more at the nodes than elsewhere. Can this be seen in 

 the stem examined ? 



Observe the enlargement and thickening at the nodes, and split one of 

 these lengthwise to see whether the tissue within it is exactly like that in 

 the internodes. How may the difference, if any, be explained ? 



Compare with the corn-stalk a piece of palmetto ^ and notice the simi- 

 larity of structure, except for the fact that the tissue in the palmetto 

 which answers to the pith of the corn-stalk is much darker-colored and 

 harder than corn-stalk pith. Compare also a piece of rattan. 



Cut a thin cross-section of the corn-stalk, examine with a moderately 

 high power of the microscope, and note : 



(o) The rind, composed largely of hard, thick-walled fibres known as 

 sclerenchyma fibres ; 



(6) The fibro-vascular bundles, most abundant near the outside, 

 becoming much more scattered toward the centre of the stem ; 



(c) The pith, occupying the intervals between the fibro-vascular 

 bundles. 



1 The pieces wliioli are sold at the druggists' prepared for nail-brushes will serve 

 the purpose well. 



