ISO 



THE STEM PROPER 



295. — Vertical sec- 

 tion of cornstalk : g, 

 groove ; c, cortex ; 

 v^ fibrovascular bun- 

 dles mingled with 

 parenchyma ; b, bud ; 

 n, node. 



Structure of the stalk you will understand why this groove 

 should occur on the side of an internode bearing a bud 

 or fruit. 



Cut a cross section midway between 

 two nodes, and observe the composition 

 of the interior; of what does the bulk 

 of it appear to consist .^ Notice the 

 arrangement of the little dots like the 

 ends of cut-off threads that are scattered 

 through the pith ; where do they appear 

 to be most abundant, toward the center 

 or the circumference .' 



Make a vertical section through one of 

 the nodes. Cut a thin slice of the pith, 

 hold it up to the light, and 

 examine it with a hand 

 lens. Observe that it is 

 composed of a number of tiny oblong 

 compartments or cells packed together 

 like bricks in a wall. These are dry and 

 empty now, but in the living stem were 

 filled with nourishing fluids consisting of 

 protoplasm and cell sap (Sec. 9), and 

 formed what is known to botanists as the 

 parenchyma, a word meaning parent tis- 

 sue, because from it all the other tissues 

 are derived. 



Draw out one of the woody threads run- 

 ning through the pith. Break away a bit 

 of the epidermis and see how very closely 

 they are packed on its inner surface. 

 Trace the course of the veins in the bases of the leaves 

 that may be found clinging to some of the nodes ; find 

 their point of union with the stem ; with what part of 

 it do they appear to be continuous ? Has this anything 

 to do with the greater abundance of fibers near the epider- 

 mis } Can you follow the fibers through the nodes, or do 

 they become confused and intermixed with other threads 



296. — Vertical sec- 

 tion of a portion of 

 the interior of a dry 

 cornstallc as seen un-. 

 der the lens, showing 

 the cellular structure 

 of the parenchyma : 

 -0, fibrovascular bun- 

 dles ; /, pith, or 

 parenchyma. 



