326 Dr. J. W. Dawson on Spore-cases in Coals. 



1. The mineral charcoal, or '' mother coal," is obviously 

 woody tissue and fibres of bark, the structure of the varieties 

 of which and the plants to which it probably belongs I have 

 discussed in the paper above mentioned. 



2. The coarser layers of coal show under the microscope a 

 confused mass of fragments of vegetable matter belonging to 

 various descrijjtions of plants, and including, but not usually 

 largely, sporangites. 



3. The more brilliant layers of the coal are seen, when se- 

 parated by thin laminae of clay, to have on their surfaces the 

 markings of SigiUarice and other trees, of which they evidently 

 represent flattened specimens, or, rather, the bark of such spe- 

 cimens. Under the microscope, when their structures are 

 preserved, these layers show cortical tissues more abundantly 

 than any others. 



4. Some thin layers of coal consist mainly of flattened layers 

 of leaves of Cordaites or Pycnophyllum. 



5. The Stigmaria-ixnderclajs and the stumps of Sigillaria 

 in the coal-roofs equally testify to the accumulation of coal by 

 the growth of successive forests, more especially of SigiUarice. 

 There is, on the other hand, no necessary connexion of spo- 

 rangite-beds with Stigmarian soils. Such beds are more likely 

 to be accumulated in water, and consequently to constitute 

 bituminous shales and cannels. 



6. Lepidodendron and its allies, to which the spore-cases in 

 question appear to belong, are evidently much less important 

 to coal-accumulation than Sigillaria, which cannot be affirmed 

 to have produced spore-cases similar to those in question, 

 even if the observation of Goldenberg as to their fruit can be 

 relied on — the accuracy of which, however, I am inclined to 

 doubt. 



On the whole, then, while giving due credit to Prof. Huxley 

 and those who have preceded him in this matter, for directing 

 attention to this curious and, no doubt, inq^ortant constituent 

 of mineral fuel, and admitting tliat I may possibly have given 

 too little attention to it, I must maintain that sporangite-beds 

 are exceptional among coals, and that cortical and woody 

 matters are the most abundant ingredients in all the ordinary 

 kinds ; and to this I cannot think that the coals of England 

 constitute an exception. 



It is to be observed, in conclusion, that the spore-cases of 

 plants, in their indesti-uctibility and richly carbonaceous cha- 

 racter, only partake of qualities common to most suberous 

 and epidermal matters, as I have explained in the publications 

 already referred to. Such epidermal and cortical substances 

 are extremely rich in carbon and hydrogen, in this resembling 



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