CHAPTER I 



ROOTS AND RHIZOMES 



Some fifty-five roots, rhizomes, and rhizomes and roots are 

 official in the pharmacopoeia and national formulary. About 

 5 of these are obtained from monocotyledonous plants, and 

 50 from dicotyledonous plants. 



In studying the structure of roots and rhizomes, then, it 

 must first be determined whether the root m question is mono- 

 cotyledonous or dicotyledonous. This fact is ascertained by 

 determining the type of the fibro-vascular bundle. The bundle 

 is of the open collateral type in all rhizomes and roots obtained 

 from monocotyledonous plants, but it is closed, radial, or con- 

 centric in the monocotyledonous t^-pe. 



In both of these groups the cellular plan of structure is 

 similar, the chief variation being the absence of one or more 

 types of cells, the variation in the amount, in arrangement, in 

 the anatomical structure, in the color, and in the cell contents 

 of the individual cells. These facts will be impressed on the 

 mind while studying the rhizomes and the roots. 



CROSS-SECTION PINK ROOT 



The cross-section of pink root (Plate 89) has the following 

 structure : 



Epidermis. The epidermal cells are small, nearly as long 

 as broad, and the outer wall is thicker and darker in color than 

 the side and inner walls. The cells usually contain air. 



Cortex, The cortical parenchyma cells are very large and 

 somewhat rounded in outline, and the walls are white. There 

 are about twelve rows of these cells, and each cell contains 

 numerous small, rounded starch grains. 



Endodermis. The endodermal cells are tangentially elon- 

 gated, and the walls are very thin and white. There are two 

 or three layers of endodermal cells; the cells' outer layers are 

 larger than the cells of the inner layers. 



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