IV. STIGMARIA STRUCTURE. BY HENRY S. POOLE, F. R. S. C. 



F. G. S., &c. 



(Read March 18th, 1901.) 



The specimen of Stigmaria here exhibited is from the Coal 

 Measures at Stellarton, and from a fireclay bed between two of 

 the working coal seams. The original fragment, about 9 inches 

 long and 3.5 by 2.25 in cross-section, was given to the Geological 

 Survey Museum with a preferred right to a section should the 

 piece ever be cut. This was done on the advice of the Director, 

 the late Dr. Dawson. who also sent another section to Mr. 

 Kidston of Stirling, Scotland. 



The special interest in the specimen, lies in the exceptionally 

 well preserved condition of the heart or medulla due to infiltration, 

 the whole root having been converted into clay ironstone. The 

 piece here shown presents a cross section only of the beautifully 

 preserved scalariform tissue of the medulla which is placed below 

 the centre of the root and nearest the concave underside. Mr. 

 Kidston in his acknowledgment to Dr. Dawson, remarked that 

 the section was one of considerable interest from a botanical 

 point of view, shewing more numerous and finely radiating 

 wedges of vascular tissue than other stigmaria roots he has lately 

 been studying. 



Stigmaria, when first found, were considered a distinct g^nus 

 but are now known to be but the roots ot Sigillaria. The late 

 Mr. R. Brown of Sydney Mines, Cape Breton, found in the cliffs 

 near the pits a tree trunk that clearly showed the passage of the 

 Sigillaria stem into the Stigmaria roots, and similar specimens 

 have been found elsewhere. 



The Sigillaria, Mr. Carruthers describes as consisting of a 

 central cellular pith or medulla surrounded by a sheath consist- 

 ing wholly of scalariform vessels, the whole enveloped in an 



(345) 



