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FOSSIL PLANTS. 



A great amount of labour, no doubt, has still to be devoted to the study of the 

 structure of many of our common Coal-measure Plants before we can speak on all 

 points with positive certainty. 



II. General Observations on Sigillaria, Anabathra, Diploxylon, and 



Stigmaria. 



Ever since the time when the Fossil Plants of the Coal-measures first attracted 

 attention, Sigillaria has occupied a chief place in the minds of botanists ; for it is to be 

 met with in the strata near most seams of coal, in a more or less perfect state of preser- 

 vation. The trunks of this genus are of two kinds, namely, those distinctly ribbed and 

 furrowed, with leaf-scars on the ribs at greater or less distances, and those with the leaf- 

 scars contiguous, and covering the whole surface of the trunk ; both having them in a 

 spiral arrangement around the axis. Nearly one hundred species have been described 

 by different authors, who have made numerous species out of the same trunk ; various 

 parts of it being in a bad or good state of preservation. No doubt, when we are better 

 acquainted with the true nature of the plant, the number of species will be greatly 

 reduced. 



For a long time Sigillaria and Stigmaria were regarded as distinct genera of plants, 

 and even now, on the Continent, some distinguished palaeontologists are disposed to 

 remain of that opinion. In the specimens first described by me, in the ' Philosophical 

 Magazine ' for 1844, 1 which were found in Mr. Littler's quarry, near St. Helen's, 

 Stigmaria was clearly traced to the trunks of the large, irregularly ribbed and furrowed 

 Sigillaria, showing little, if any, traces of leaf-scars ; but it was there distinctly stated 

 that around these trunks smaller trunks were found standing, which showed all the 

 characters of Sigillaria reniformis, with Stigmaria rootlets in the adjoining strata, 

 pointing in the direction of the root, but not absolutely proved to be connected with it. 

 On viewing the specimens as they originally stood in the quarry before their removal, 

 little doubt could be entertained as to all the trees there found having had Stigmaria 

 for their roots. In some specimens, however, afterwards described by me in the 

 'Philosophical Magazine' for 1847, ser. 3, vol. xxxi, p. 259, the connection of 

 Stigmaria, as a root, with Sigillaria reniformis, S. alternans, and S. organum, was 

 clearly proved. 3 



The regularly ribbed and furrowed Sigillaria, with distinct leaf-scars, generally found 

 flattened and compressed in the sandstones and shales, are seldom of so large a size as 



' 'Phil. Mag., ser. 3, vol. xxiv, p. 10'8 ; and 1845, vol. xxvii, p. 241, &c. 

 2 See also 'Quart. Journ. of Geol. Soc.,' vol. ii, p. 391. 



