242 PLANT-LIFE 



course of Palaeozoic times, and there are no modern 

 plants which would lead us to suspect their existence in 

 the past. So far as our knowledge goes, it seems to 

 indicate that the Sphenophylls did not form an exten- 

 sive group, but their fossil remains are of great interest 

 in that they demonstrate the existence of a plant group 

 intermediate between the Horsetails and Lycopods. 

 The genus Sphenophyllum (Gr. sphen, a wedge; phyllon, 

 a leaf) was dominant in the group, its earliest traces 

 being found in Upper Devonian strata. The fossils 

 indicate delicate stems, probably of climbing habit, 

 and it has been suggested that the plants scrambled 

 over other vegetation, using it as a support, in much 

 the same way as is exhibited in our modern Bedstraws— 

 for example, the Goosegrass, or Cleavers (Galium af- 

 arine). The stems were ribbed, and furnished with 

 whorls of leaves at considerable intervals The leaves 

 were commonly, but not invariably, wedge-shaped, 

 generally six in a whorl, and attached by their points 

 to the stem. The fructifications were in the form of 

 cones, resembling somewhat those of Calamites. The 

 Psilotaceae (p. 163) are considered to be what may be 

 called a modern suggestion of this ancient group. Pos- 

 sibly the Lycopods, Sphenophylls, and Equisetales 

 evolved from a common ancestry, of which we have 

 no fossil record; but where full evidence is lacking, 

 we can only speculate, and it were unwise to dogma- 

 tize. 



We have a unique knowledge of the vegetation of the 

 Carboniferous Period, because of the rich fossiliferous 

 character of the Coal Measure deposits. The wealth of 

 fossil plants obtained from these deposits must not, 



