238 



PLANT-LIFE 



The name Stigmaria has been given to fossil roots, 

 which are frequently found in situ in the " under clay " 

 below coal-seams. Fig. 75 depicts a stump with at- 

 tached roots found in Yorkshire, and preserved in the 

 University Museum in Manchester. The diameter of 

 the stump is 4 feet 4 inches, and the root-spread is 

 about 30 feet. In the absence of fossil remains other 



Fig. 74. — Sigillaria mamtllaris : Part of Stem-Surface. 

 l.s., Leaf-scars; c.s., cone-scars. Note vertical ribs. 



than the roots classed as Stigmaria, it seems impossible 

 to determine whether they belonged to Sigillarice or 

 Lefidodendra. 



Modern Equisetales, or Horsetails (p. 157), all em- 

 braced in the genus Equisetum, are the living repre- 

 sentatives, but few in number, yet by no means lacking 

 in virility, of a great race of plants which were highly 

 developed and very numerous in Palaeozoic times. 

 Indeed, in the history of the Equisetales we have an 

 example of a race's degeneration — that is, if it be 



