1865. J DAWSOX — COAL-FORMATION. 133 



regard to the mode of attachmeiit of these fruits, I have shown that one 

 species, T^ngonocarpum racemosum of the Devonian strata*, was borne 

 on a rhachis in the manner of a loose spike, and I am convinced that 

 some of the groups of inflorescence named Antholithes are simply young 

 Khahdocarpi or Trigonocarpa borne in a pinnate manner on a broad 

 rhachis and subtended by a few scales. Such spikes may be regarded 

 as corresponding to a leaf with fruits borne on the edges, in the 

 manner of the female flower of Cycas ; and I believe with Goldenberg 

 that these were borne in verticils at intervals on the stem. In this 

 case it is possible that the strobiles described by that author may be 

 male organs of fructification containing, not spores, but pollen. In 

 conclusion, I would observe that I would not doubt the possibility that 

 some of the fruits known as Cardiocarpa may have belonged to 

 Sigillarioid trees. I am aware that some so-called Cardiocarpa are 

 spore-cases of Lepidodendron ; but there are others which are mani- 

 festly winged nutlets aUied to Trigonocarpum, and which must have 

 belonged to phsenogams. It would perhaps be unwise to insist 

 very strongly on deductions from what may be called circumstan- 

 tial evidence, as to the nature of the fruit of Sigillaria ; but the 

 indications pointing to the conclusions above stated are so numerous 

 that I have much confidence that they will be vindicated by com- 

 plete specimens, should these be obtained. (Figs. 29 and 30, PI. YII., 

 and figs. 69 to 79, PI. XII.) 



All of the Joggins coals, except a few shaly beds, afford unequivo- 

 cal evidence of Stigmaria in their underclajs ; and it was obviously 

 the normal mode of growth of a coal-bed, that, a more or less damp 

 soil being provided, a forest of SigiUa7na should overspread this, and 

 that the Stigmarian roots, the trunks of fallen Sigillarice, their leaves 

 and fruits, and the smaller plants which grew in their shade, should 

 accumulate in a bed of vegetable matter to be subsequently converted 

 into coal — the bark of Sigillaria and allied plants afl'ording " bright 

 coal," the wood and bast tissues mineral charcoal, and the herbaceous 

 matter and mould dull coal. The evidence of this afi'orded by micro- 

 scopic structure I have endeavoured to illustrate in a former paper f. 



The process did not commence, as some have supposed, by the 

 growth of Stigmaria in ponds or lakes. It was indeed precisely the 

 reverse of this, the Sigillaria growing in a soil more or less swampy 

 but not submerged, and the formation of coal being at last arrested 

 by submergence. I infer this from the circumstance that remains 

 of Cyprids, Fishes, and other aquatic animals are rarely found in the 

 underclays and lower parts of the coal-beds, but very frequently in 

 the roofs, while it is not unusual to find mineral charcoal more 

 abundant in the lower layers of the coal. For the formation of a 

 bed of coal, the sinking and subsequent burial of an area previously 

 dry seems to have been required. There are a few cases at the 

 Joggins where Calamites and even Sigillarice seem to have groAvn on 

 areas liable to frequent inundation ; but in these cases coal did not 

 accumulate. The non-laminated, slickensided and bleached condition 

 of most of the underclays indicates soils of considerable permanence. 



* " Flora of the Devonian Period," Quart. Journ. Greol. Soc. vol._viii. p. 324. 



t " On the Structures in Coal," Quart. Journ. Greol. Soc. 1859. 



VOL. XXII. PART T, L 



