248 
THE ROOT 
hidden). Each of these parts of 
a root adapts it to do its work. 
The epidermis keeps it from dry¬ 
ing. The region of the cortex 
contains the conducting vessels 
which carry water to the stem 
and digested food back. The 
central cylinder is the region 
where most of the food is stored. 
The root cap protects the tender 
end of the root from injury as it 
pushes through the soil, and the 
meristem tissue provides for re¬ 
newing all the regions of the root, 
and increasing their size. Besides 
the main root, there are many 
smaller roots which divide still 
Figure 235-Cross and Long.- further into rootlets. The root 
tudinal Section of Root. and its divisions underground 
may be compared, in a general 
way, to the stem, branches, and twigs aboveground. 
218. Root Hairs. — Root hairs are found a short distance 
back from the tip of each rootlet. 
Each hair consists of a projection 
of an epidermal cell. Root hairs 
are very numerous. As the root 
grows, the hairs farthest from the 
tip die and are replaced by new 
ones nearer the tip. Root hairs 
greatly increase the absorbing 
surface of a rootlet. They attach 
themselves firmly to particles of 
soil from which they are able to 
, , , . „ Figure 236. — Longitudinal 
take almost every trace of mois- Section through Root and 
ture by the process of osmosis (see Root Cap. 
