CHAPTER X. 



THE ANATOMY OF THE STEM, ROOT, AND LEAF. 



We propose in the present chapter to discuss the general 

 arrangement and structural character of the various ordinary 

 tissues in the different plant organs and incidentally to mention 

 their uses in the economy of the plant leaving the more detailed 

 account of physiological processes for subsequent chapters. 



THE STEM. 



A. The Herbaceous stems of dicotyledons. 



A great portion of the herbaceous stems of dicotyledons consists 

 of soft succulent tissue, in which are imbedded a number of 

 thin, tough, stringy strands termed vascular bundles. The latter 

 give firmness to the stem, but their chief function is the conduc- 

 tion of sap to all parts of the plant. y^o 



Covering the surface of the stem ^__ 

 is a thin skin or tissue of cells called 

 the epidermis. To the remainder of 

 the tissues, that is, to all except the 

 epidermis and vascular bundles, the 

 X&x'Oi fundamental or ground tissue is 

 applied. 



In a transverse section of the stem disttfbutio7o°?h^e^chief tfssue's"in the 

 the vascular bundles are seen to be :',\?„t\tdS^s!?cor'/exf>riufi:1 

 arranged side by side in a circle »' n'^duiiaxy rays. 

 (Fig. 53). That part of the fundamental tissue enclosed by the 

 ring of vascular bundles is spoken of as the medulla or pith (p), 

 the part outside the ring is the cortex (c), while the small narrow 



H "3 



