And, what is more, real live fairies have been found right down in the world of roots! The science people call them "Bacteria," but what of that? The thing about a fairy that makes it a fairy is that it is always changing something into something else. Isn't that right? Well, that's exactly what is done by the bacteria on the roots of certain kinds of plants--clover roots, for one; and the roots of beans, peas, peanuts, and alfalfa. These plants belong to the legume family, and if you will look up the word _Legumes_ you will find out all about these fairy factories on the roots. Among other things you'll learn how small these fairies are. Why, 100,000 of the bacteria that live on clover roots, marching single file, wouldn't much more than reach across this typed page.[24] And in their little "villages" on one system of clover roots there are so many that all of them put together would make a city as big as London or New York; if the bacteria were as big as people, I mean. [24] By the way, the funny thing is that, while the bacteria that live on roots of the legumes are plants and not animals, most of them _do_ move about. Of course you have to take a microscope to see them--a very powerful microscope--and even then some kinds of bacteria you can't see until you put colored clothes on them. (Every high school boy who has worked in the "lab" knows how this is done.) And when you finally see them, a strange thing happens. You've hardly got your eye on a little Mr. Bacteria before he's two! "What's this! What's this!" you say. "Am I seeing double?" You look again and he's _four_! But don't be alarmed, you aren't seeing double; it's just the little Mr. Bacterias multiplying by division. How they multiply by division is one of the interesting things you can learn by looking them up. But it's a good thing that the bacteria people in the little nitrogen factories on the clover roots can get more farm-hands in this way, for they have a lot to do, and their work is one of the most interesting things that goes on about the place. The article in the "Country Life Reader" on "The Smallest Plant on the Farm" will tell you how important these nitrogen farmers are. You would hardly believe how great their work is, they're so quiet about it. Do you know what a human nitrogen factory is like? Well, for one thing, it's the _noisiest_ place in the world. Men, as do the bacteria, capture the nitrogen out of the air, but they do it by keeping up continual thunder and rain storms in big barrels. You will find one of these factories described in an article in _St. Nicholas_, Volume 45, page 1137.