222 GEOLOGY. 



are represented in Fig. 123, b being the same with a, but 



Fig. 123. 



showing remains of its roots. The plant is jointed and 

 hollow, the surface being deeply fluted. While the 

 rushes and cat-tails of the present day are quite small, 

 some specimens of these ancient plants have been found 

 20, and even 40 feet in length, and three feet in diameter. 

 Portions of the trunks of these trees, for so they may be 

 called, have been found standing upright in coal mines, 

 penetrating the sandstone layers above the coal. 



321. Sigillaria and Stigmaria. These were for a long 

 time supposed to be two distinct plants, but they have 

 been found to belong to the same plant, the Sigillaria be- 

 ing the trunk, and the Stigmaria the lower part of the 

 trunk, with the roots. The Stigmaria, Fig. 124, is never 

 found any where but in the under clay spoken of in 

 310. The trunks of the plant are generally found lying 

 horizontally, but sometimes they are erect. They vary in 

 length from five to sixty feet, and in diameter from a 

 few inches to five feet. 



