THE ROOT. 
53 
seed represents the offspring of the plant and contains 
an embryonic plant consisting of three more or less 
distinct parts, which are more easily differentiated 
after germination. 
If we take the seed of a pea or bean or other flower- 
ing plant, and surround it with conditions favorable to 
its germination and growth, it is soon observed that 
one part of the young plant invariably grows down- 
ward, unless there is some obstruction, and this is 
known as the root. Connected with this is another part 
which usually grows in an opposite direction, and this 
is known as the stem. Upon the latter are developed 
parts called leaves. The first leaves formed are 
known as seed leaves, and if they are two in number 
the plant is known as a dicotyledon, whereas if there 
is only one seed leaf, the plant is called a mono- 
cotyledon. 
The root or descending axis of the plant is popu- 
larly supposed to grow downward, in order to avoid 
the light. The roots of plants grown in flanging bas- 
kets, however, naturally emerge into the light, and 
then continue their downward growth. On the other 
hand, it is supposed by many (as a result of Knight’s 
experiments) that the root grows downward by reason 
of the influence of gravity. In addition it may he said 
that the principal functions of the root, namely, those 
of preparing and absorbing inorganic food materials, 
and of fixing the plant to the soil, determine in a 
measure the direction of its growth. The tendency of 
the root to grow downward is a characteristic which 
distinguishes it from other parts of the plant and is 
known as positive geotropism. 
If we take a germinating plant and mark the root 
lengthwise, by means of a fine pen and India-ink, into 
ten equal divisions, beginning at the apex, and place 
