HOW PLANTS FEED 27 
level in the jar will gradually sink. The small tube, will 
enable the diminution in volume to be seen by a class 
during the progress of a lesson. The water level in the 
tube at the beginningof the lesson should be marked by 
means of a small piece of white paper gummed round the 
tube. 
Plant Food must be dissolved in Water.— 
(a) Ifa plant be placed in water containing insoluble 
salts of all the chemical elements required by the plant 
it will be found that the roots will absorb the water, but 
that the salts will remain as a powder in the vessel, and in 
a short time the plant will cease to grow. 
(b) Tf two plants be taken and one be placed so that its 
roots will dip into water holding eosin in solution, and 
those of the other into water containing red particles of 
carmine, which do not dissolve, it will be found that, 
whereas the red colour of the eosin has found its way 
into the roots and up the stem, the particles of carmine 
remain suspended in the water and no colour passes into 
the root. 
Experiment } will also show—in the case of the eosin 
solution—that plant food dissolved in water enters the 
root and passes up through the stem and branches to 
the leaves. 
Black ironsand found in such abundance round our 
coasts will provide an excellent insoluble substance for 
one of the experiments. 
Path of Current up the Stem. The following 
experiment will show that the liquid passes up the 
woody part of the stem. 
Place a branch bearing leaves in a vessel of water as 
shown, having previously cut a ring of bark from the 
stem. The bark should be cut right down to the wood, 
