346 STIGMARIA 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 medullarv 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 
rounded, 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 centr] pith surrounded by 
a sheath of sealariform vessels, the wh Je 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 photugraphs 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 
pithy 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™™ 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™™ and 60™™ An approxi- 
mately concentric crack-like line partly infiltrated with whitish 
material runs around more than two-thirds of the periphery> 
about 4™™ from the edge, suggesting an exterior bark layer. 
