Plants of Past Ages. 353 



softer coals still give clear evidence of their origin, for they 

 appear to be chiefly the carbonized masses of the stems 

 and leaves of ferns, Lycopods, and Calamites (see Fig. 192). 

 Even those coals which have been so much altered from 

 their original condition that the naked eye is unable to 

 detect their vegetable origin are found by means of the 



Fig. 192. 



Carboniferous Plants. In the foreground on the left Lepidodendrons and Sigillarias 

 (relatives of the modern Lycopods) ; just back of these Calamites, with branches 

 in whorls (relatives of the modern horsetails). On the right tree ferns; in the 

 background, in addition to the foregoing, Cordaites (low with upright leaves). 



microscope to contain the cells and tissues of plants. 

 Many of the ferns of this period attained the size of trees, 

 and the Lepidodendrons reached a height of 50 to 75 feet. 

 The Lycopods, as many as eighty species of which have 

 been found, also grew to great size. The Calamites, which 

 are near relatives of the modern horsetails, also attained 

 great proportions and apparently occupied the inundated 



