14S PKOCEEDINGS OE THE GEOLOGICAL SOCIETY. 



broader than the oval or elliptical tripunctate areoles, and are striated 

 longitudinally. The woody axis has both discigerous and scalariform 

 tissues, arranged in wedges, with medullary rays as in exogens ; 

 the pith is transversely partitioned in the manner of Sternbergia ; 

 and the inner bark contains great quantities of long and apparently 

 very durable fibres, which I have, in my descriptions of the structures 

 in the coal, named ' bast-tissue.' The outer bark was usually thick, 

 of dense and almost indestructible cellular tissue. The trunk, when 

 old, lost its regular ribs and scars, owing to expansion, and became 

 furrowed like that of an old exogenous tree." 



It will be understood that this statement refers to the main stems 

 of the libbed jSigillarice of the type of S. reniformis and S. Brownii, 

 so abundant in the coal-formation of Nova Scotia, and that it is made 

 with especial reference to the conditions of the accumulation of coal 

 in that province. The evidence on which it is based may be stated 

 under the foUomng heads : — 



Erect Trunks. — The numerous erect stumps of SigiUarice occur- 

 ring at the South Joggins, and at Sydney, Cape Breton, are usually 

 preserved as casts in sandstone, the only part of their organic sub- 

 stance remaining being the outer bark, which exists in the state of 

 compact coal. StiU the interior structures have not altogether pe- 

 rished, but may be recognized as a layer of mineral charcoal in the 

 bottom of the stony column, under the sand and other foreign mat- 

 ters subsequently introduced. Occasionally the bark of the tree has 

 collapsed before it could be filled with sediment, and the only re- 

 mains of the trunk consist of the little mound of carbonaceous mat- 

 ter derived from the tree itself. Cases of this kind are mentioned 

 in my paper on the South Joggins*. In addition to the coaly mat- 

 ter showing structure, we can also occasionally find in the interior of 

 such erect trees a transversely striated sandstone cast (Sternbe7'gia) 

 representing the medullary cylinder. In one instance only have I 

 found the medullary cylinder calcified in such a manner as to show 

 its structure, and surrounded by the woody cylinder also in a calci- 

 fied state. This specimen was that described, but not adequately 

 figured, in my paper on the Structures in Coal,- and I now propose 

 to figure it more in detail (Plate X.), Ordinarily the coaly mass 

 consists of confused fragments of mineral charcoal derived from 

 the wood and the fibrous tissues of the bark ; but these often retain 

 their structure very perfectly. 



After collecting and examining the woody matter thus remaining 

 in twenty or more of these erect trees, I have found that, with one 

 exception, it consists of tissues of a uniform character, presenting 

 only such diff'erences as might be expected in trees generically 

 allied. The tissues observed are discigerous or porous wood-cells with 

 from one to four rows of pores, pseudo-scalariform tissue, and elon- 

 gated structureless cells of the bark (the "bast-tissue" of my former 

 papers). These structures indicate that the woody parts of these 

 trees were identical in character with those of the calcified axis 

 above-mentioned. 



* Quart. Journ. Geol. Soc. vol. x. p. 1. 



