THE ROOT 6S 
69. Root pull.— Roots are not mere passive holdfasts, 
but exert an active downward pull upon the stem. Notice 
the rooting end 
of astrawberry or 
raspberry shoot 
and observe how 
the stem appears 
to be drawn into 
the ground at the 
rooting point. 
In the leaf ro- 
settes of herbs 
growing flat on 
the ground or in 
Fie. 83. — Dandelion : a, common form, grown in plains 
region at low altitude ; b, alpine form. 
the crevices of walls and pavements, the strong depression 
observable at the center is due to root pull. (Fig. 84.) 
¥ 1c. 84.— Raspberry sto- 
lon showing root pull. 
70. Storage of food. — Another of- 
fice of roots is to store up food for the 
use of the plant. This is done chiefly 
in the tissues of fleshy roots and tu- 
bers, and gives to them their great 
economic value. Next to grains and 
cereals, roots probably furnish a larger 
portion of food to the human race 
than any other crop. In addition to 
this they are also the source of valu- 
able drugs, condiments, and dyes. 
71. Absorption and conveyance of 
sap. — But the most important func- 
tion of roots is that of absorption. 
By their action the soil water and the 
minerals contained in it are drawn up 
into the plant body and made avail- 
able for conversion by the leaves into 
organic foods, as will be explained in another chapter. From 
the nature of their function, most roots have naturally a 
