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 in 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 type. 
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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