98 THE OPEN BOOK OF NATURE 
plants. Spores also occur, but you will need long 
practice in the practical study of fossil plants before 
you can make them out. 
Plant remains occur in greater variety in the 
Devonian rocks. If you have access to the strata 
of this Period you must keep your eyes open for 
fossil seaweeds, ferns, club-mosses, horse-tails, as 
well as remnants of yews and pines. 
But the fossil-plant collector finds a happy 
hunting-ground among the rocks of the Carboniferous 
Period. There he can find remains of the huge club- 
mosses, horse-tails and tree-ferns, which were evi- 
dently the principal features of the plant-life of 
those days. Existing club-mosses are dwarfs com- 
pared with their Carboniferous relations ; nowadays 
they never exceed three or four feet in height, 
and most of them are very much smaller ; but then 
they attained a height of fifty, and perhaps sixty, 
feet, and formed great forests. The Lepidodendron 
(Greek, lepidotus=scaly, and dendron=tree) was 
one of the commonest of those giant club-mosses. 
You can find traces of it in rubbish thrown out of 
coal-pits, and in quarries or cuttings in sandstones 
of Carboniferous age. The stems and branches 
which you find in fossil state are covered with 
lozenge-shaped scars, which mark the places from 
whence the stiff grasslike leaves had dropped. Or 
very often you find impressions of the plant on the 
rocks. I know of no more common or more interest- 
ing fossil plant. The Calamites (Latin, calamus=a 
reed) of the Carboniferous times grew to the size of 
forest trees. Of course, you know the modern 
horse-tail plant; if you do not, get someone to 
