1 82 THE FAIRY-LAND OF SCIENCE. 
20 feet high, whereas the little Equisetum, Fig. 52, is 
seldom more than a foot, and never more than 4 feet 
high in England, though in tropical South America 
they are much higher. Still, if you have ever gathered 
" horsetails," you will see at once that those trees in 
the foreground of the picture (Fig. 51), with leaves 
arranged in stars round the branches, are only larger 
copies of the little marsh-plants ; and the seed-vessels 
of the two plants are almost exactly the same. 
These great trees, the Lepidodendrons, the Sigil- 
larias, and the Calamites, together with large tree- 
ferns and smaller ferns, are the chief plants that we 
know of in the coal-forests. It seems very strange at 
first that they should have been so large when their 
descendants are now so small, but if you look at our 
chief plants and trees now, you will find that nearly 
all of them bear flowers, and this is a great advantage 
to them, because it tempts the insects to bring them 
the pollen-dust, as we saw in the last lecture. 
Now the Lepidodendrons and their companions 
had no true flowers, but only these seed-cases which 
we have mentioned ; but as there were no flowering 
plants in their time, and they had the ground all to 
themselves, they grew fine and large. By-and-by, how- 
ever, when the flowering plants came in, these began 
to crowd out the old giants of the coal-forests, so 
that they dwindled and dwindled from century to 
century till their great-great-grandchildren, thousands 
of generations after, only lift up their tiny heads in 
marshes and on heaths, and tell us that they were big 
once upon a time. 
And indeed they must have been magnificent in 
