Water and the Plant 77 
long as the plant lives 
and is active, the root 
system continues to 
branch and send out a 
mass of young rootlets. 
When their limit of depth 
and breadth is reached, 
branches continue to fill 
in the space between 
with a network of the 
fine roots. 
A short distance be- 
hind the tip of a rootlet 
there is a growth some- 
what resembling cotton 
fibers. If we look at this 
with a reading glass or 
a simple pocket mag- 
nifying glass, we find 
that this is composed of 
delicate hair-like out- 
growths from the root 
itself. Each of these 
root hairs is a slender 
tube that has grown out - 
from the side of a cell. 
Fic. 46. Young radish seedling with soil 
clinging to root hairs. The root hairs 
penetrate among the soil particles and 
drain off the water from them. 
It is a rod-shaped structure, 
closed like a finger of a glove at its outer end, and by 
its growth it thrusts itself in among the soil particles 
_and absorbs water and mineral compounds in solution. 
In this way the absorbing surface of the rootlet is enor- 
mously greater than if no root hairs were developed. 
