PA 

THE ROOT 195 
The part of the cortex outside of the endodermis is frequently 
composed of parenchyma cells only. These cells may serve for 
the slow movement and storage of food. As in the case of stems 
the cortex in young roots is of importance in giving rigidity. 

Fie. 192. Cross section of root of mungo bean (Phaseolus radiatus) older 
than that shown in Fig. 189 
e€, epidermis ; c, cortex; en, endodermis: , pericycle; ca, cambium region ; 
ph, phloém ; px, protoxylem ; mz, metaxylem. (x 85) 
This is done by means of turgor. The epidermis of the root is 
usually an ephemeral structure. In many cases the cell walls 
of the outer layers of the cortex become thickened, and these 
layers take the place of the epidermis. 
The cortex of the root does not contain collenchyma, as does 
that of many stems. In stems the collenchyma usually forms a 
