But how could all these things get there?
Why, if we cannot find them in the air to be absorbed by the leaves, they must be in the soil or ground. Now, it so happens that those substances are to be found in different quantities in different places.
How do they get into the plant, father?
Simply by the little rootlets absorbing small particles of them, mixed with moisture.
But do all plants require the same amount of lime, potash, soda, and the others?
No, my dear. There are not two sorts of trees that feed upon the same materials in exactly the same proportions.
Is that the reason, then, why some land is so much better fitted to grow one plant than another?
The reason is, because the one soil has more of the right sort of food in it.
Now I see that if I wanted to grow a good crop of any thing, I must give it plenty of the food it likes best.
Yes, but not too much. For like as too much nice rich food is bad for children, so it is with vegetables: ground may be too rich, as well as too poor.