156 THE FAIRY-LAND OF SCIENCE. 
And now the plant can no longer afford to be idle 
and live on prepared food. It must work for itself. 
Until now it has been taking in the same kind of 
food that you and I do ; for we too find many seeds 
very pleasant to eat and useful to nourish us. But 
now this store is exhausted. Upon what then is the 
plant to live ? It is cleverer than we are in this, for 
while we cannot live unless we have food which has 
once been alive, plants can feed upon gases and water 
and mineral matter only. Think over the substances 
you can eat or drink, and you will find they are nearly 
all made of things which have been alive : meat, vege- 
tables, bread, beer, wine, milk ; all these are made from 
living matter, and though you do take in such things 
as water and salt, and even iron and phosphorus, 
these would be quite useless if you did not eat and 
drink prepared food which your body can work up 
into living matter. 
But the plant, as soon as it has roots and leaves, 
begins to make living matter out of matter that has 
never been alive. Through all the little hairs of its 
roots it sucks in water, and in this water are dissolved 
more or less of the salts of ammonia, phosphorus, 
sulphur, iron, lime, magnesia, and even silica, or flint. 
In all kinds of earth there is some iron, and we shall 
see presently that this is very important to the plant. 
Suppose, then, that our primrose has begun to drink 
in water at its roots. How is it to get this water up 
into the stem and leaves, seeing that the whole plant 
is made of closed bags or cells ? It does it in a very 
curious way, which you can prove for yourselves. 
Whenever two fluids, one thicker than the other, such 
