l6o THE FAIRY-LAND OF SCIENCE. 
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 phos- 
phorus, 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, sul- 
phur, 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 your- 
selves. Whenever two fluids, one thicker than the 
other, such as molasses and water for example, are 
only separated by a skin or any porous substance, they 
will always mix, the thinner one oozing through the 
skin into the thicker one. If you tie a piece of bladder 
over a glass tube, fill the tube half-full of molasses, and 
then let the covered end rest in a bottle of water, in 
a few hours the water will get in to the molasses and 
the mixture will rise up in the tube till it flows over the 
