26 NEW ZEALAND NATURE-STUDY BOOK 
al 
leaves into the stem, and are either used at once by the 
growing plants or are stored up in the stem, root, or leaves, 
for future use. 
The food which finds its way up the stem consists chiefly 
of the elements, oxygen, hydrogen, nitrogen, phosphorus, 
and sulphur ; and the combining of these elements into sub- 
stances suitable for the nourishment and support of the 
plant is known as assimilation. 
Foop OBTAINED FROM THE SOIL. 
Absorption of Food (water and inorganic salts) 
by the root-hairs.—The organs which absorb water 
are the roots. If water be supplied to the leaves and stem 
of a plant, and the soil at the same time 
be kept dry, the plant will gradually 
wither. This proves that the shoot is 
unable to absorb sufficient water. 
Fasten a piece of water-tight material 
over a pot, in which a plant is growing, 
in such a way as to prevent any water 
from entering the soil, and water the 
plant daily. It will be found, notwith- 
standing this treatment, \ 
that the plant will grad- EEN 
ually wither. | Sale 
Fig. 22, It is not a difficult eens |EZ 
' matter to show that — DL. 
the roots absorb water. Place a plant in 
a jar of water as shown. Insert a 
small tube through the cork, and by 
pressing the cork further into the jar, 
force the water up the small tube. If 
the air of the room be warm, the roots 
will rapidly absorb the water and the 
