A PIECE OF COAL. 
181 
can read it as we read a book. For example, at S 
and L, where stems are cut across, he can learn ex- 
actly how they were built up inside, and compare 
FIG. 51. Contents of a coal-ball. (Carruthers.)* S, Stem of 
Sigillaria cut across. Z, Stem of Lepidodendron cut across. 
Z', Stem of Lepidodendron cut lengthways. /, Cone of 
Lepidodendron (Lepidostrobus) cut across. C, Stem of Cala- 
mite cut across, c, c, c, Fruit of Calamite lengthways and 
across, f, Stem of a fern with fragments of fern-leaves 
scattered round it. The small round dots scattered here 
and there are the larger spores which have fallen out of the 
fruit-cones. 
* I am much indebted to Mr. Carruthers, of the British 
Museum, for allowing me to copy this figure from his original 
diagram of a coal-ball, and also for giving me much valuable 
assistance. 
