PAST HISTORIES OF PLANT FAMILIES 133 



phytes, which is not yet bridged firmly enough for any 

 but specialists, used to the hazardous footing on such 

 structures, to attempt to cross it. Until the buttresses 

 and pillars of the bridge are built of the strong stone of 

 fossil structures we must beware of setting- out on what 

 would prove a perilous journey. 



In the Coal Measures and previous periods we see 

 the ferns already represented by two large families, 

 differing greatly from each other, and from the main 

 families of modern ferns which sprung at a later date 

 from some stock which we have not yet recognized. 

 But though their past is so obscure, the palaeozoic ferns 

 and their allies throw a brilliant light on the course of 

 evolution of the higher groups of plants, and the gulf 

 between ferns and seed-bearing types may be said to 

 be securely bridged by the Botryopterideae and the 

 Pteridosperms. 



CHAPTER XIV 



PAST HISTORIES OF PLANT FAMILIES 



VII. The Lycopods 



The present-day members of this family are not at 

 all impressive, and in their lowliness may well be over- 

 looked by one who is not interested in unpretending- 

 plants. The fresh green mosslike Selaginella grown by 

 florists as ornamental borders in greenhouses and the 

 creeping " club moss " twining among the heather on a 

 Highland moor are probably the best known of the living 

 representatives of the Lycopods. In the past the group 

 held a very different position, and in the distant era of 

 the Coal Measures it held a dominant one. Many of 

 the giants of the forest belonged to the family (see fron- 

 tispiece), and the number of species it contained was very 

 great. 



