116 PIIOCEEDINOS OF SOCIKTIES. 



coal, Dr. Balfour thought it well to examine the plants which formed the flora of the coal epoc^h ; 

 these were chiefly Acrogens and Gymnosperms, the Ibrmer predominating. Of five hundred coal 

 plants mentioned by Brogniart, three hundred and forty-six appeared to have been Acrogenous 

 species, and one hundred and thirty-five Gymnosperms. He alluded to the remarkable character 

 of the fern flora of the coal epoch, which resembled that of islands such as New Zealand, where 

 the ferns were described as social plants, forming forests, to the exclusion of other plants. The 

 Acrogens in structure di3pla3'ed a large quantity of cellular tissue, some prosenchymatous tissue, 

 and scalariform vessels. In many of the coal plants allied to ferns the texture was described 

 as loose, the vascular tissue only occurring at certain definite spots, and the transverse and 

 longitudinal section of the cellular part of the stem being nearly similar. This Acrogenous floi-a 

 seemed to have contributed to the formation of coal, specimens being in fact seen in which 

 stigmarias and sigillarias were actually formed into coal. Gymnosperms, no doubt, also contributed, 

 but Dr. Balfour thought it by no means proved that they were the only plants that did so, 

 facts seeming rather to lead to the conclusion that both Acrogens and Gymnosperms had con- 

 tributed to form coal, and that, as in peat at the present day, cellular plants might also have 

 been mingled with them. In one coal basin certain tribes of plants might predominate, in 

 another basin a difierent tribe, and thus arise different varieties of coal. 



While a certain similiarity of structure existed among the parrot coals, the brown, Methil, 

 and the Boghead gas-coal appeared to occupy a special position, being very similar in appear- 

 ance and qualities, and both containing a large amount of yellow matter deposited, apparentlj', 

 in an organic basis, consisting of circumscribed cavities of different sizes, which might possibly 

 be altered cells. It was impossible to demonstrate the cellulose of the cell wall, and no one 

 would expect, as Dr. Bennet had hinted, to find the primordial utricles and nuclei in such 

 circumstances, the changes induced having altered the cell contents, and their place being now 

 occupied with yellow matter. The Methil coal was stated to belong to the same seam as the 

 Wemyss parrot coal, which differed from it in many respects, thus showing that varieties occur 

 even in the same bed. These varieties might be traced to peculiar local floras, or to chemical 

 and mechanical causes of various kinds, which induced alterations in the cells and their contents. 

 The quantity of carbon in the ]5oghead coal was said to be small, but in making the calculation, 

 the yellow matter had been discarded, which, as a product of the coal plants, it ought not to 

 have been. In Methil coal the amount of carbon, when similarly estimated, was also small; 

 the chemical analysis of brown Methil and of the Torbanehill coal being very similar; nor was 

 it easy to separate them by any definition. He therefore regarded them as mere varieties, vari- 

 ties, however, which a practised eye might be able to discriminate by the microscope, as Dr- 

 Bennet had stated, but this did not militate against their being mere varieties. Besides the 

 yellow matter, the Torbanehill mineral contained scalariform tissue, sometimes entire, sometimes 

 broken up in the same way as Corda had figured the tissue of stigmaria. Dr. B. thought that 

 the vegetable tissue did not appear to be a mere accidental admixture, but to be in reality part 

 of the Acrogenous plants which helped to form the coal. The existence of the tissue at certain 

 points only might be expected in coal formed of such plants, and the presence of peculiar 

 inflammable matter was by no means uncommon among ferns and Lycopodiacea of the present 

 day. In coals there were found certain brownish rings, which Dr. Bennet considered to be char- 

 acteristic, and to be the cut extremities of tubes; they had not, however, been traced. If tubes, 

 they must be similar to the dotted ducts, and not to the woody fibres, and this would tend to 

 prove that the tissue was not that of Coniferoe. 



Dr. Balfour was disposed to look upon these rings as being sections of sporangia or spores, 

 and similar bodies had been seen in most coals, and among others in the Torbanehill coal. [Dr. 

 Bennet, however, denied that they were spore cases or .seeds, as they were of a different size 

 from such bodies, as usually seen in coal.] Professor Balfour thought that the amount and nature 

 of the tissue required to constitute coal had certainly not been determined. In the coke of the 

 Torbanehill coal, Mr. Quekett had found a considerable amount of vegetable tissue. This seemed 

 to be an important fact which had been omitted by Dr. Bennet. [In reply, we understood Dr. 

 Bennet to say that he had not been able to corroborate the fact.] In regard to the occurrence 

 of structure in the ashes. Dr. Balfour thought that little stress could be laid upon it, as much 

 depended upon the extent to which the coal was burnt; and the inflammable nature of the 

 Torbanehill coal might cause the combustion of the tissue to be more complete than in other 

 coals. In conclusion he stated that he considered the Torbanehill coal to be a cannel coal, nearly 



