346 STIGMAIilA STRUCTURE POOLE. 



external cortical mass of cellular tissue. The medullary sheath 

 is perforated by meshes for the passage outwards of the vascular 

 bundles which go to the aerial appendages (the leaves and 

 branches), but there are no true medullary rays. Hence he 

 classes the Sigillaria as Cryptogamic and Lycopodiaceous. 



The external surface of Stigmaria is without the vertical and 

 parallel fluting between the pits or shallow tubercles distinctive 

 of the Sigillaria, and in this particular specimen the pits are 

 rounder), depressed and widely separated and not sharply defined. 

 No rootlets were attached. When found the fire-clay bed had 

 weathered away from the specimen. 



The internal structure exhibits a central pith surrounded by 

 a sheath of scalariform vessels, the wh >lo enclosed in a cellular 

 envelope. Dr. A. H. MacKay, our President, kindly undertook 

 to examine this specimen, and I am glad to be able to append 

 his description with reproductions of photographs of magnified 



portions of the section. 



I would merely add that it is now believed that such piths as 

 this specimen illustrates have, when separated from their 

 envelope, given rise to fossils classed as Sternbergia, which are 

 described as comprising cylindrical transversely marked casts of 

 pith}' cylinders of other plants, belonging chiefly to conifers, but 

 referable also to sigillaria. 



Dr. MacKay s Description of the Section. 



The section is transverse, about 21 mm thick, black, with infil- 

 trations of brown to white in some crack-like lines, and is 

 polished where cut. This polished black surface (clay iron- 

 stone) can be scratched by the point of a hard steel knife, but 

 does not effervesce under a drop of hydrochloric acid. The 

 whitish infiltrated lines referred to effervesce as if calciferous. 



The contour of the section is an irregular oval with rectan- 

 gular axes respectively about 95 mm and 60 mm - An approxi- 

 mately concentric crack-like line partly infiltrated with whitish 

 material runs around more than two-thirds of the periphery, 

 about 4 mm from the edge, suggesting an exterior bark layer. 



