ROOTS ARE PUMPS 
to be none. Each of these root hairs, under the micro¬ 
scope, is seen to be a hollow tube. Each goes its way, 
feeling around among the gravel or grains of dirt for what 
moisture it can get. A pebble taken out of the ground is 
likely to be damp. It is, in fact, covered with a film of 
water. So are all the grains in damp soil. These tiny 
root hairs are able to suck up that water and start it up¬ 
ward. Every one of them in the darkness underground 
is gathering up this water that is scattered so very thinly 
through the soil. The amount of water that one rootlet 
gathers is very small indeed, but there are so many of 
them working at the task that the total that the roots of 
a single tree gather in a day may amount to many 
barrels. 
This water, pumped up into the leaves and combined 
with the carbon dioxide from the air, makes the sugar 
that is the plant’s chief food. But the roots also gather 
from the ground various minerals that are carried up with 
the water, and that serve a purpose in tree-building. 
Anybody who wants to can grow himself a plant which 
will develop root hairs that all may see. He has but to 
plant some grains of wheat or some radish seed on a flat 
cork floating in a jar of water and let it stand in a sunny 
window. The plant will grow up, and the roots will grow 
down. They will develop the structure in the water that 
they would develop in the ground and give an exhibition 
of what a plant has working for it underground. 
29 
