lO o 
86 
The Life of the Wheat Plant from Seed to Seed. 
scutellum has modified some of the starch, and in the further pro- 
cess of mashing the bruised malt, the work begun in the germi- 
nating grain is completed, and the whole of the starch is con- 
verted into grape sugar. The maltster kills the germinating 
seed by raising the temperature of his kiln above 104° Fahr. 
The young plant, dried up and rubbed off, is known as comings 
or malt dust. 
In another three days the roots have actively exteJided 
themselves, and have developed a number of fine hairs, which 
supply a large surface for taking in the needed water. There 
10 are no openings in the roots for the entrance of water ; it is 
taken in through the walls of the root hairs. Dissolved in it 
the wheat-plant secures some mineral and other substances 
necessary for its food, such as compounds of nitrogen, potash, 
lime, magnesia, silica, iron, phosphorus, and sulphur. In his 
use of different mineral and other manures, the farmer supplies 
the necessary substances in which the field is deficient, or re- 
places those that have been removed by former crops. 
G The leaves are still covered by the protecting sheath, and 
new ones are being formed at the growing point of the stem. A 
7 transverse section shows the cell structure of the protecting 
sheath, and the first green leaf folded up on itself. The leaf is 
8 covered by a skin or epidermis, which encloses a mass of green 
cells, penetrated by slender fibres (vascular bundles) passing up 
9 the leaf, and forming the veins. These fibres (which are the leaf 
skeleton) form the supporting framework for the cell tissue and 
also serve to transmit fluids. The epidermis is pierced by nume- 
rous two-lipped mouths (stomates) to permit the entrance of the 
air to the green cells, and the escape of water-vapour and the 
gases set free by the plant. 
III. The Young Pl^vnt. 
{The figures prin'eil in the marejin refer to the corresponding figures on page 94.) 
1 In twelve days or so after sowing, the first green leaf makes 
2 its appearance. The little plant has grown about an inch high. 
The point of the leaf pushes itself through the sheath and at 
once begins to manufacture food on its own account, though 
3 there still remains for its use a large stock of food in the seed. 
The stomates which are seen in the unexpanded leaf admit the 
air to the green cells. Atmospheric air is a mixture of the two 
gases, oxygen and nitrogen, with some water and a small quantity 
of carbonic acid gas. This gas forms rather less than one part in 
every two thousand : it is the portion of the air which the plant 
requires for food, and it is the function of the leaf to obtain it. 
During sunlight the protoplasm in the green cells of the leaf is 
