466 THE CARBONIFEROUS SYSTEM. 



acid, I liave found that the structures remaining both in the lustrous 

 compact coals and in the bark of Sigillarice are parenchymatous cells 

 and fibrous cells, probably bast-fibres. 



7. I by no means desire to maintain that all portions of the coal- 

 seams not in the state of mineral charcoal consist of cortical tissues. 

 Quantities of herbaceous plants, leaves, etc., are also present, especially 

 in the coarser coals ; and some small seams appear to consist entirely of 

 such material, — for instance, of the leaves of Cordaites or Foacites. I 

 would also observe that, though in the roof-shales and other associated 

 beds it is usually only tlie cortical layer of trees that appears as compact 

 bituminous coal, yet I have found specimens which show that in the 

 coal-seams themselves true woody tissues have sometimes been im- 

 bedded unchanged, and converted into structureless coal, forming, 

 like the coniferous trees converted into jet in more modern for- 

 mations, thin bands of veiy pure bituminous material. The pro- 

 portion of woody matter in this state differs in different coals, and 

 is probably greatest in those which show the least mineral char- 

 coal ; but the alteration which it has undergone renders it almost 

 impossible to distinguish it from the flattened bark, which in all 

 ordinary cases is much more abundant. 



II. In the mineral charcoal, which affords the greater part of the 

 material showing distinct vegetable structures, the following kinds 

 of tissue are those ordinarily observed : — 



a. Bast tissue, or elongated cells from the liber or inner bark of 

 Sigillarife and Lepidodendron, but especially of the former. — This 

 kind of tissue is abundant in a calcified state in the shales associated 

 with the coals, and also as mineral charcoal in the coals themselves, 

 and in the interior of erect Sigillarice. It is the kind of tissue figured 

 by Brongniart as the inner layer of bark in Sigillaria elegans, and very 

 well described by Binney (Quart. Journ. Geol. Soc. vol. xviii.) as 

 " elongated tissue or utricles." Under the microscope many specimens 

 of it closely resemble the imperfect bast tissue of the inner bai-k of 

 Finns strobus and Thuja occidcntalis ; and like this it seems to have 

 been at once tough and durable, remaining in fibrous strips after 

 the woody tissues had decayed. It is extremely abundant at the 

 Joggins in the mineral charcoal of the smaller coal-seams. It is 

 often associated with films of structureless coal, which represent 

 the dense cellular outer bark which, in the trunk of Sigillaria, not 

 only surrounded this tissue, but was intermixed with it. 



b. Vascular bundles of Ferns. — These may be noticed by all close 

 observers of the surfaces of coal, as slender hair-like fibres, sometimes 



