vol. 63.] xerophytic characters of coal-planis. 291 



Discussion. 



The President referred to the long-standing controversy as to 

 whether coal-seams were formed of plants which grew on the spot 

 among swamps, or of vegetation that had been washed away from 

 drier ground. As in most scientific disputes, there was truth on 

 both sides. He thought that there could be no doubt that in a 

 large number, perhaps the majority, of cases the coal-seams repre- 

 sent a flora that grew on the spot where its remains are now pre- 

 served, and that the areas of growth were shallow lagoons or 

 swamps to which the sea had access. The evidence of the remains 

 of fishes and marine shells regularly intercalated and perfectly pre- 

 served among the shales and coal-seams, showed that the swamps 

 were connected with the sea, and the proofs of quiet and regular 

 sedimentation gave no countenance to the idea of violent inundations 

 of the sea upon a terrestrial surface. It was satisfactory to know, 

 from the testimony of palaeobotanists, that there was nothing in the 

 internal structure of the coal-plants contradictory of the belief that 

 these plants had their roots submerged under salt water. On the 

 •other hand, it had long been recognized that the Carboniferous 

 strata contain abundant remains of drifted vegetation, some of 

 which may have grown on dry land. How far it might be possible 

 to discriminate between the lagoon-plants and those which flourished 

 inland remained to be determined. 



Prof. Seward referred to the different opinions expressed as to 

 the conditions under which the plants of the Coal-Period grew, more 

 particularly to the suggestion of the late Mr. Binney, favourably 

 received by Charles Darwin, that some at least of the plants grew 

 in salt-marshes. The speaker considered that the evidence of 

 anatomy seemed to lend support to the salt-marsh hypothesis. He 

 did not agree with the Author's conclusions ; and, while welcoming 

 discussion on the subject, he believed that it was somewhat pre- 

 mature to attempt to make definite statements as to the habitats 

 of the plants of the Carboniferous flora. Palaeobotanists had con- 

 stantly before them the bearing of anatomical evidence on the 

 ■ question of habitat ; and he expressed the opinion that further 

 research into the anatomy of Palaeozoic plants would go far towards 

 supplying an answer to the questions dealt with by the Author. 



Prof. F. "W. Oliver said that it was probably premature to 

 dogmatize as to the conditions under which any plant had grown, 

 from a consideration of its anatomical features alone; and this 

 applied with especial force when different sorts of xerophytism 

 were considered. Investigations into tissue-function and plant- 

 ecology generally had as yet been carried out so locally and on so 

 restricted a scale, that he could only describe this branch of study 

 as being still in its infancy. A recent discussion upon the water- 

 requirements of the trees of temperate and tropical countries, 

 respectively, had served to emphasize this point. 



Before it was possible to generalize about the Coal-Measure 

 plants, it would be necessary to reconstruct the flora of those times. 



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