28 
THE ROOT. 
30. Structure of the Root. — ^The Eoot {radix) is the basis 
of the plant, or that part which usually enters the earth, and 
extends in a direction contrary to the growth of the stem ; it 
originates with the radicle of the seed, supports the plant in an 
upright position, and at the same time gives nourishment to 
every part of it. There are exceptions to the general fact of a 
root being fixed in the ground ; some plants, as the pond-lily, 
frow in water, and are q,21\q^ aquatio ; some, like the mistletoe, 
ave no root, but fix themselves upon other plants, and derive 
sustenance from them; such are cdiiX^di pan^asites.^ 
The root consists of the ca/iidex^ the main body of the root ; 
fibrils^ the finer branches, which are the true roots ; and the 
spongioles^ extremities of the root, which are composed of cel- 
lular tissue, and ducts or mouths, which absorb nutritious 
■juices. The nourishment ascending through the stem expe- 
riences in the leaves and green parts of the plant an important 
change, effected, in part, through the agency of air and light ; 
and a portion of it, through a different set of vessels, flows 
back, in what is called the returning sap, or cambium. The 
nourishment thus digested is returned to the stem and root, 
and is expended in the formation of new rootlets and branches. 
The downward direction of the root is accounted for by the 
delicacy of the fibers, w^hich causes them to shun the light and 
air, and also by the effects of gravitation, which they have not 
the force to resist. The summit of the root, or that part which 
connects it with the ascending axis, is called the collum^ or 
neck ; any injury to this part is followed by the death of the 
plant. 
31. Duration of Roots. — Roots, with respect to duration^ 
are a/nnual^ biennial^ ov perennial. 
Annual Boots live but one year. They come from the seed 
in the spring, and die in autumn, including such as are raised 
from the seed every year ; as peas, beans, cucumbers, &c. The 
flowering process and the maturing of the fruit exhaust the 
plant, and having no nourishment accumulated in its dry 
nbrous root, it perishes as soon as its seed is perfected. Bien- 
nial Boots live two years. They do not produce any flowers 
the first season ; the next summer they blossom, the seeds 
mature, and the roots die. The roots of cabbages are often, 
after the first season, preserved during the winter. In the 
spring they are set out in gardens, and produce flowers ; the 
ovary grows into a pod which contains the seed. The root 
• The word parasite, from the Greek para, with, and sitos, corn, was first applied to those who had 
Ihe care of the corn used in religious ceremonies, and were allowed a share of the sacrifice ; afterward it 
was applied to those who depended on the great, and earned their welcome by flattery. 
30. The root— Parts of the root —31 Annual roots— Biennial. 
