720 



THE WONDERS OF GEOLOGY. Lect. VII. 



enabled to ascertain the relations of these remarkable 

 extinct trees with recent forms. From this examination 

 it results that the Sigillariae were a family of coniferous 

 trees, belonging to the great division of gymnospermous 

 dicotyledons. In their external form they must have some- 

 what resembled the Cacteae, or Euphorbiae, but were more 

 nearly related by their internal organization to the Zamiae 

 and Cycadeae.* Their leaves and fruits are unknown, for 

 no certain connexion has yet been established between 

 these stems and the foliage and fruit with which they are 

 collocated, f 



37. Stigmaria. — The fossil vegetables known under this 

 name, which are so abundant in the underclay of the coal- 

 beds, have long excited the curiosity of collectors, and set at 

 defiance all attempts to determine their botanical charac- 

 ters, until recent discoveries proved the correctness of M. 

 Adolphe Brongniart's conjecture, that they were the roots 

 of Sigillariae. These bodies are of a cylindrical form, from 

 a few inches to several feet in length, and are often ten or 

 twelve inches in circumference. The surface is covered 

 with oval or circular depressions with a small tubercle in the 

 middle, disposed in quincunx order. When broken across, 

 a small cylindrical axis or core is found to extend longi- 

 tudinally throughout the stem, like a medullary column. 

 When observed in the underclay, long tapering fibres or 

 rootlets are found attached to the tubercles of the pits with 

 which the surface is covered ; and these are sometimes 

 several feet in length. The internal structure of the Stig- 

 marice presents a ligneous zone resembling that of the 



* The stems of some of the Sigillariae, when uncompressed, remind 

 one of the longitudinally furrowed cylindrical columns of the Pilo- 

 cereus senilis, which grow so luxuriantly, and many feet in height, 

 in Real del Monte, in Mexico. There are fine living specimens of this 

 form of Pilocereus, in the Royal Botanic Gardens, at Kew. 



f See Medals of Creation, p. 135. 



