122 ELEMENTARY BOTANY 
Take two healthy seedlings (Wallflower is 
convenient), keep one with its roots in dis- 
tilled. water, the other with its roots in Water culture solu- 
tion. 
Experiment IV. 
The first does not thrive, and after a time dies ; 
the second flourishes. (Compare Figs. 141, 142.) 
A plant requires something besides water on 
which to live, and as the substances in the water 
culture solution are present in most soils, it is clear that the 
_ plant gets from the soil not only water, but lime, potash, ete. 
It is true that plants often grow when seeds are supplied 
only with tap-water, as those of the bean or pea. The reason 
is that these seeds contain a great deal of food in their coty- 
ledons, and tap-water is not pure water. 
Plants must have for tood: Nitrogen, sulphur, phosphorus, 
chlorine, potassium, calcium, magnesium, iron, carbon, oxygen, 
hydrogen. And that this is the case may be proved experi- 
mentally by growing plants in water culture solution, from 
which one or other of these substances has been omitted. It 
will be found, if any one is omitted, that the plant does not 
thrive, and may even die. 
Take two plants with uninjured roots, and 
place one in water in which there has been 
put afew drops of eosin; place the other plant in water con- 
taining powdered carmine. 
The eosin which dissolves is taken in, and if 
the stem of the plant is cut across, the wood will 
be seen to be coloured. The carmine is not dissolved, is not 
taken into the plant, and the wood is not coloured. 
Plants can absorb only those substances which 
are in solution. 
We may now sum up the chief facts with regard to the 
food obtained by the plant from the soil. The first necessity 
is water, for no solid can be taken in as solid, it must be 
in solution in order to be absorbed, and able te pass through 
the cells of the plant. Further, water is an essential con. 
stituent of the protoplasm and cell-wall. 
Result. 
Conclusion. 
Experiment V. 
Result. 
Conclusion. 
