THE FAIRY-LAND OF SCIENCE. 
on the left-hand side of the coal-forest picture, having 
those curious tufts of leaves springing out of them at 
the top. Their stems 
make up a great deal oi 
the coal, and the bark 
of their trunks is often 
found in the clays above, 
squeezed flat in lengths 
of 30, 60, or 70 feet. 
Sometimes, instead of 
being flat the bark is 
still in the shape of a 
trunk, and the interior is 
filled with sand; and 
then the trunk is very 
heavy, and if the miners 
do not prop the roof up 
well it falls down , and 
kills those beneath it. 
Stigmaria (Fig. 50, page 
178) is the root of the 
FIG. 54. Equisetum or horsetail. . ., , . . 
Sigillana, and is found 
in the clays below the coal. Botanists are not yet 
quite certain about the seed-cases of this tree, but Mr. 
Carruthers believes that they grew inside the base of 
the leaves, as they do in the quillwort, a small plant 
which grows at the bottom of mountain lakes in Eu- 
rope and America. 
But what is that curious reed-like stem we found 
in the piece of shale (see Fig. 49) ? That stem is very 
important, for it belonged to a plant called a Calamite, 
which, as we shall see presently, helped to sift the 
