CHAPTER XVIII 
THE ROOT 
The root is the part of the plant which grows from the 
bottom of the stem. The roots of most plants are under¬ 
ground. Roots are the part of the plant that (1) gather 
water and food material from the soil; (2) that hold the 
plant firmly in the soil, 
and (3) in plants that 
live over the winter, store 
food to be used the fol¬ 
lowing year. 
217. Structure of a 
Root. — The outer part 
of the root is covered 
with a layer of epidermis 
called dermatogen (der- 
mat'o-jen: Greek, derm, 
skin). Inside of this is a 
region called the cortex 
or periblem (per'i-blem: 
Greek, peri, around) 
which surrounds the in¬ 
nermost region called the 
central cylinder or ple- 
rome (pler'om: Greek, plere, full). Near the tip, below 
the central cylinder, is a rapidly growing tissue, the meristem 
(mer'i-stem: Greek, meristos, divided), from which all the 
other parts develop. Over the end of the smaller roots is 
the root cap or calyptrogen (kal-ip'tro-jen: Greek, kalyptros, 
247 
Figure 234. — Cross Section of Root 
with Root Hairs. 
Note the relation of the hairs to the 
epidermal cells. Note also the irregu¬ 
larity caused by growth among the parti¬ 
cles of soil, some of which still adhere. 
