10 STRUCTURAL BOTANY 



palaeontology, and are of the greatest possible import- 

 ance, because they enable us to a certain extent to 

 trace the past history of the different kinds of plants. 

 To take only one example : the enormously rich vegeta- 

 tion which is so well preserved in the coal-measures con- 

 sisted of forms of plants which have long since become 

 extinct. The classes to which many of the great trees 



FIG. 5. Stump and roots of a Fossil Tree (Stigmaria ficoidcs) 

 from the carboniferous sandstone. The diameter of the 

 stump is 4 ft. 4 in., and the spread of the roots 28-30 

 ft. (After Williamson.) 



of that period belonged (such as the Stigmaria figured) 

 are now only represented by a few small herbaceous 

 plants (such as Selayinella). 1 On the other hand, 

 most of the groups which are now of the greatest 

 importance had not then appeared, and their first 

 representatives are found in much later rocks. 2 This 



1 See Part II., Flowerless Plants, p. 1. 



2 See Jukes's School Manual of Geoloyy, p. 280. 



