J. W. Daicson on Spore cases in Coals. 261 



(6.) Lepidodendron and its allies, to wliicli the fpoi-e-easos in 

 question appear to belong, are evidently much less imj^ortant 

 to coal accumulation than Sigillaria, which cannot be affirmed to 

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

 though the observation of Groldenberg as to their fruit can be 

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



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 important constituent of 

 mineral fuel, and admitting that I may possibly have given too 

 little attention to it, I must maintain that Sporangite boils are 

 exceptional among coals, and that conical imd voody matters 

 are the most abundant ingredients in all the onlinarv kinds; 

 and to this I cannot think that the coals of England constitute 

 an exception. 



It is to be observed, in conclusion, that the spoi'c-cases of 

 plants, in their indestructibility and richly carbonaceous char- 

 iicter, only partake of qualities common to most suberous and 

 epidermal matters, as I have explained in the publications al- 

 ready referred to. Such epidermal and cortical substances are 

 extremely rich in carbon and hydrogen ; in this resembling bi- 

 tuminous coal. They are also very little liable to decay, and 

 they resist more than other vegetable matters aqueous infiltra- 

 tion; properties whicb have caused them to remain unchanged 

 and to resist the penetration of mineral substances more than 

 other vegetable tissues. These qualities are well seen m the 

 bark of our American white birch. It is no wonder that mate- 

 rials of this kind should constitute considerable portions of such 

 vegetable accumulations as the beds of coal, and that when 

 'resent in large proportion they should aflPord richly bituminous 

 ^ds. All this agrees with the fact, apparent on examination 

 0^ the common coal, that the greater number of its purest layers 

 consist of the flattened bark of Sigillarite and similar trees, just 

 as any single flattened trunk imbedded in shale becomes a layer 

 of pure coal. It also agrees with the fact that other layers of 

 coal, and also the cannels and earthy bitumens appear, under 

 the microscope, to consist of finely comminuted particles, pnnci- 

 Pally of epidei-mal tissues, not only from the fi-uits and spore- 

 cases of plants, but also from their leaves and stems. The same 

 considerations impress us iust as much as the abundance of 

 spore-cases, with the immense amount of the vegetable matter 

 ^aich has perisbed during the accumulation of coal, m com- 

 parison with that which has been preserved. . 



I am indebted to Dr. T. Sterry Hunt, for the following very 

 valuable information, which at once places in a clear and pre- 

 cise light the chemical relations of epidermal tissue and spores 



pres( 

 beds 



