THE FERN ALLIES. 7 



bers and importance. The prototypes of our lowly 

 club-mosses and scouring-rushes — the lepidodendrons, 

 sigillarias, and calamites — often equalled in size the 

 forest trees of the present, and their remains form the 

 greater part of the Coal Measures. It is reported that 

 one of the Scottish coal beds consists almost entirely of 

 the spores and spore-cases of some extinct Lycopodium. 

 Of our modern genera, Equisettun dates from the 

 Triassic Period ; Isoctcs, Marsilia, and Pilularia from 

 the Tertiary ; and Lycopodium from as far back as the 

 Devonian Period. 



With few exceptions the fern aUies are not remark- 

 able for either beauty or utility. Some of the club- 

 mosses, under the more familiar names of running pine 

 and trailing evergreen, are annually used in quantity for 

 holiday decorations, and various species of Selaginella 

 are cultivated for their graceful foliage. The spores of 

 the club-mosses form the lycopodium of the pharmacist 

 and have been used in the manufacture of fireworks, 

 while the rough stems of the scouring-rushes were once 

 valued for polishing and scouring. 



