On Spirally dotted Ducts in Anthracite Coal. 409 
the original organic structure, and which consequently could never 
have been reduced to a homogeneous pulp. 
2. The plants from which the coal was chiefly formed do not 
appear to have been allied either to the Conifer, or the ordinary 
Dicotyledonous or Monocotyledonous plants. Their nearest 
analogues must probably be sought among the Acotyledons, 
among which Ferns and Lycopodiacez. present similar vascular 
bundles, composed chiefly of bothrenchymatous tissue.* 
3. Even allowing for the effects of compression, it does not 
appear probable that the petioles of even the tree ferns could have 
furnished such large flattened plates of scalariform ducts unmixed 
with other tissues as are found in the coal, and which very rarely 
have any traces of fronds of ferns preserved in the same mass. 
4. It is possible that the ducts in question may really have be- 
longed to the Stigmaria itself. Lindley and Hutton, from the exam- 
ination of a magnified section of a silicified Stigmaria, pronounce 
it to be a plant whose woody portions were entirely composed of 
spiral vessels ; but their figure of these vessels, however interest- 
ing, leaves some room to suppose that spirally dotted ducts partly 
obscured by petrifaction might have been mistaken for true spiral 
vessels. (See Fossil Flora of Great: Britain, vol. iii, plate 166.) 
This view is confirmed by Unger, who attributes dotted ducts alike 
to the Stigmarie and the woody layers of Lepidodendree and 
Sigillarie. (Endl. Gen. Plant. sup. 2, pp. 5, 6.) 
5. Vascular bundles must certainly have extended from the 
sears found on the Stigmaria and Sigillaria to the deciduous ap- 
pendages, (see Foss. Flora, vol. i, plates 31, 32, and 33,) whether 
these latter were leaves or radical fibres, and the partial decay of 
masses composed of numerous layers of such appendages, would 
account for most of the appearances observed in the coal. 
6. The proofs afforded by these examinations, that the coal is 
composed of layers, of great tenuity, of vegetable matters scatter- 
ed in a confused manner, and that no trunks of trees or any con- 
siderable portion of their branches had any thing to do with its 
formation, are in exact accordance with the inferences drawn by 
Prof. H. D. Rogers, from an examination of the mechanical struc- 
ture of unburned coal.t 
* Since the above was written, I have observed that Ad. Brongniart, in a recent 
number of the Comptes Rendus, maintains that Stigmaria, Sigillaria and Lepido- 
dendron, as well as Noeggerathia, ll allied to the Gy p dicotyled 
t See Transactions of the Association of American Geologists, p. 448. 
ee 
