THE CARnONIFEROUS. 69 



thus are able to resist those atmospheric influences whicli effect the 

 decay of woody tissue.' 



" I would add to this only one further consideration. The nitrogen 

 present in the Lycopodium spores, no doubt, belongs to the protoplasm 

 contained in them, a substance which would soon perish by decay ; 

 and subtracting this, the cell-walls of the spores and the walls of the 

 spore cases would be most suitable material I'ur the production of 

 bituminous coal. But this suitableness they share with the epidermal 

 tissue of the scales of strobiles, and of the stems and leaves of ferns 

 and lycopods, and above all, with the thick corky envelope of the 

 stems of SigiUaricB and similar trees, which, as 1 have elsewhere 

 shown,* from its condition in the pro.strate and erect trunks contained 

 in the beds associated with coal, must have been highly carbonaceous 

 and extremely enduring and impermeable to water. In short, if 

 instead of 'spore-cases,' we read 'epidermal tissues in general, 

 including spore-cases,' all that Huxley has affirmed will be strictly 

 and literally true, and in accordance with the chemical composition, 

 microscopical characters, and mode of occurrence of coal. It will also 

 be in accordance with the following statement, from my paper on the 

 Structures in Coal, published in 1859 : — 



" ' A single trunk of Sigillaria in an erect forest presents an 

 epitome of a coal-seam. Its roots represent the Sligniaria underclay ; 

 its bark the compact coal ; its woody axis the mineral charcoal ; its 

 fallen leaves (and fruits), with remains of herbaceous plants growing 

 in its shade, mixed with a little earthy matter, the layers of coarse 

 coal. The condition of the durable outer bark of erect trees concurs 

 with the chemical theory of coal, in showing the especial suitableness 

 of this kind of tissue for the production of the purer compact coals. 

 It is also probable that the comparative impermeability of the bark 

 to mineral infiltration is of importance in this respect, enabling this 

 material to remain unaffected by causes which have filled those layers, 

 consisting of herbaceous materials and decayed wood, Avith pyrites 

 and other mineral substances.' " 



8. THE DEVONIAN. 



On tlio distribution and arrangement of the rocks of this period I 

 have nothing material to add to what I have already stated in refer- 

 ring to the Geological Map. Though the Devonian does not occupy 

 a very wide area in the Acadian Provinces, yet, in coiniection with 

 the neighbouring areas in the province of Quebec, it is of great in- 



* Vegetable Structures in Coal, Jour. Geol. Soc, xv. G'26. Conditions of Accumu 

 lation of Coal, j'i., xxii. 95. Acadian Ueology, l'J7, 104. 



