FOSSIL FLORA. 59 



PLATE XXI. 

 "FicoiD Stigmaria." 



{Stigmaria ficoides, of M. Brongniart, Hist. Veg. Foss. tab. 17, figs. 5, 6. 

 Ficoidites furcatus, of Mr. Artis.) 



The fossil trunks or stems called StigmaricB, or Variolce, (from the pits or areolae with which 

 they are studded,) occur as abundantly in the coal formation as the Sigillaries, of which tribe of 

 plants unequivocal proof has at length been obtained that they are the roots. These bodies 

 are more or less regularly cylindrical, and vary in length from a few inches to fifteen or twenty 

 feet, the largest being several inches in diameter. Their surface is covered with numerous 

 oval or circular depressions, in the middle of each of which there is a rounded papilla, or tubercle. 

 These variolse are disposed round the stem in quincunx order. When these roots are broken 

 across, a small cylindrical core or pith is exposed, which extends in a longitudinal direction 

 throughout the stem, like a medullary column. This central axis, which is often separable from 

 the surrounding mass, is composed of bundles of vascular tissue disposed in a radiated manner, 

 and separated from each other by medullary rays. This internal organization presents the 

 same correspondence with that of the stems of Sigillariae, as does the structure of the roots of 

 a dicotyledonous tree with that of its branches and stems. 



The Stigmarise are almost invariably present in the bed called the " Under Clay," which 

 underlies the coal, and when observed in this situation, long tapering sub-cylindrical fibres are 

 found attached to the tubercles ; and these processes or rootlets are often several feet in length. 

 Their form and mode of attachment are shown at c, d ; the rootlets terminate in bifurcations, 

 as seen at a, b. 



The specimen here figured is part of a root nearly six feet long, and three inches in diameter ; 

 some of the rootlets were two feet long. It is imbedded in shale ; from Elsecar colliery." 



' A Stigmaria with rootlets, many feet in length, is placed over the doorway in the room devoted to fossil vegetables in 

 the Gallery of Organic Remains in the British Museum. 



