19 



such axes has led me to the conclusion that there are two 

 types of these erect trees, one with an axis of scalariform 

 tissue only, 1 though with the outer radiating cylinder 

 characteristic of Diploxylon, the other with a double axis 

 of pseudo-scalariform tissue internally, and discigerous or 

 multiporous tissue externally, of similar character to the 

 stems of Gordaitece. Perhaps in accordance with this is the 

 fact which I have also illustrated, that some so called 

 Sigillarice or Favularice of the type of S. Elegans, have some- 

 what broad parallel-veined leaves resembling those of Poa- 

 cordaites. 2 



As characteristic examples of these trunks, I may refer 

 to two which I have described in the Journal of the Geo- 

 logical Society. 



(a) SIGILLARIA (Diploxylon.) 



The most characteristic example is a trunk rooted in an 

 under-clay in the Joggins section and existing as a sand 

 cast 12 feet in height. This tree was discovered and care- 

 fully removed by Mr. Albert J. Hill, who found the interior 

 of the cast a calcified axis extending throughout its length 

 and showing well preserved structure. The structure is 

 described as follows : 3 



" The axis is about 6 centimetres in its greatest diameter, 

 and consists of a central pith cylinder and two concentric 

 coats of scalariform tissue. The pith cylinder is replaced 

 by sandstone, and is about one centimetre in diameter. 

 The inner cylinder of scalariform tissue is perfectly contin- 

 uous, not radiated, and about one millimetre in thickness. 

 Its vessels are somewhat crushed, but have been of large 

 diameter. Its outer surface, which readily separates from 

 that of the outer cylinder, is striated longitudinally. The 

 outer cylinder, which constitutes by much the largest 

 part of the whole, is also composed of scalariform tissue ; 



1 Journal Geological Society of London. 



2 Acadian Geology. 



3 Journal Geological Society of London, Vol. xxxiii., 1877- , 



