A GIGANTIC FLOATING PLANT. 359 



spirally disposed tubercles, resembling the papillae at the 

 base of the spines of Echini. From each tubercle there 

 proceeded a cylindrical and probably succulent leaf; these 

 extended to the length of several feet from all sides of the 

 branches. (PI. 56, Figs. 10. 11.) The leaves, usually, in a 

 compressed state, are found penetrating in all directions into 

 the sand-stone or shale which forms the surrounding matrix ; 

 they have been traced to the length of three feet, and have 

 fbeen said to be much longer.* 



In many of the strata that accompany the coal, fragments 

 of these plants occur in vast abundance ; they have been 

 long noticed in the sand-stone called Gannister and Crow- 

 stone, in the Yorkshire and Derbyshire coal fields, and have 

 been incorrectly considered to be fragments of the stems of 

 Cacti. 



The discovery of the dome-shaped centres above de- 

 scribed, and the length and forms of the leaves and branches 

 render it highly probable that the Stigmarise were aquatic 

 plants, trailing in swamps, or floating in still and shallow 

 lakes, like the modern Stratiotes and Isoetes. From such 

 situations they may have been drifted by the same inunda- 

 tions, that transported the Ferns and other land vegetables, 

 with which they ai^e associated in the coal formation. The 

 form of the trunk and branches shows that they could not 

 have risen upwards into the air ; they must therefore either 

 have trailed on the ground, or have floated in water. J The 



sion there is found a loose internal eccentric axis, or woody core (PI. 56. 

 Fig. 10. a.) surrounded with vascular fasciculi that communicated witii the 

 external tubercles, and resembled the internal axis within the stems of cer- 

 tain species of Cactus, 



* All these are conditions, which a Plant habitually floating with the 

 leaves distended in every direction, would not cease to maintain, when 

 drifted to the bottom of an Estuary, and there gradually surrounded by 

 sediments of mud and silt. 



•j- The place and form of the leaves, supposing them to have grown on 

 all sides of branches suspended horizontally in water, would have been 

 but little changed by being drifted into, and sinking to the bottom of, an 



