CHAPTER XVI. 



Sigillaria. 

 i. General. 



In view of the close resemblance between Lepidodendr&n 

 and Sigillaria, another lycopodiaceous plant characteristic of 

 Carboniferous and Permian floras, a comparatively brief de- 

 scription of the latter genus must suffice, more particularly as 

 Lepidodendron has received rather an undue share of attention. 

 Sigillaria, though abundantly represented among the relics of 

 Palaeozoic floras, especially those preserved in the Coal- 

 Measures, is rare in a petrified state, and our knowledge of its 

 anatomy is far from complete. In external form as in internal 

 structure the difference between the two genera are not such as 

 enable us to draw in all cases a clearly defined line of separation. 



In the Antediluvian Phytology, Artis^ figured a fossil from 

 the Carboniferous sandstones of Yorkshire which he called 

 Euphorbites vulgaris on account of a superficial resemblance 

 to the stems of existing succulent Euphorbias. Rhode^ also 

 compared Sigillarian stems with those of recent Cacti. The 

 specimen described by Artis is characterised by regular vertical 

 and slightly convex ribs bearing rows of leaf-scars in spiral series, 

 like those on the cushions of Lepidodendron. A few years earlier 

 Brongniart' had instituted the genus Sigillaria* for plants with 

 ribbed but not jointed stems bearing" disc-like impressions" (leaf- 

 scars) disposed in quincunx; the type-species named by the author 

 of the genus Sigillaria scutellata is identical, as Kidston'' points 



1 Artis (25) A. PI. xv. 2 Ehode (20). 



3 Brongniart (22) A. PI. xii. fig. 4. 



* For generic names wholly or in part synonymous with Sigillaria, see 

 White (99) p. 230. 



6 Kidaton (86) A. p. 186. 



