87 
The Life of the Wheat Plant from Seed to Seed. 
actively laying bold of tbe molecules of carbonic acid gas, and 
breaking them up to obtain the necessary carbon. The oxygen 
which is not required is returned to the air, while the carbon is 
manufactured into stai’ch by union with oxygen and hydrogen, 
which have been obtained as water from the soil. 
When the plant has risen about four inches above the ground 4 
the second leaf makes its appearance. A longitudinal section 
of the plant at this time shows that a lateral bud has already 5 
been formed, which will in due time develop into a stem bearing 
its own ear of grain. The buds from which the secondary stems 
in a wheat plant grow are formed at the base of the older leaves, 
in the angle between the leaf and the stem. They are repetitions 
of the main stem, except that it sent its roots into the ground, 
while these are at first implanted on the original stem, though 
afterwards they send out roots of their own. Nearly the whole 
store of food has now been used up. The delicate cells at the 
tip of the stem are adding fresh joints and forming new leaves. 
After a few days a third leaf appears. The whole of the food 6 
laid up by the parent has been utilised, and the plant has now 
to manufacture all its food. The roots have increased in 8 
number, and are beginning to branch. 7 
The root increases in length by growing at its extremity. 9 
This is a special adaptation to the conditions under which it has 
to live. It has to push its way between the particles of the 
soil. Having insinuated itself thi’ough the smallest opening, 
it then easily pushes aside the particles of the soil as it grows 
in thickness. 
IV. Early Growth of the Ear. 
i^The figures printed in the margin refer to the corresponding figures on page 95.) 
A longitudinal section of a young plant of wheat, with only 1 
four leaves spread out, shows that all the joints that exist in the 
straw of the full-grown plant are already formed, and that each 2 
joint has its own proper leaf sj^ringing from it. Above the last 
leaf the stem terminates in a small knob, which is the beginning 
of the ear. A month later many additional stems have been 3 
produced, and a corresponding development of the roots has 
taken place. A transverse section of such a plant near the root 
shows the original stem near the centre, and two or more se- 4 
condary stems, each with still younger stems springing from 
their bases. The production of stems beyond the primary one 
is greatly helped by securing for each plant a fair space to grow 
upon. This increase of stems from one seed, called tillering, 
may proceed until as many as fifty or more are produced, each 
with its head of grain. A longitudinal section shows the short 5 
