168 PROF. W. C.WILLIAMSON ON THE STRUCTURE 



corresponding tracts^ composed of masses of a peculiar 

 form of woody fibre,, with one large medullary ray in the 

 centre of each tract. 



My friend Mr. Binney has thrown further light upon 

 this subject in his volume ^ On the Structure of Calamites 

 and Calamodendron^\ which only came into my hands 

 after the previous pages had been written. Mr. Binney 

 does not attempt to separate Calamites from Calamoden- 

 dron, but contents himself with describing his specimens^ 

 which are of great interest. The woody cylinder of every 

 one of them essentially resembles that examined by linger^ 

 in consisting of radiating alternate tracts of barred or scal- 

 ariform vessels^ and of coarse cellular tissue. This copious 

 development of scalariform vessels demonstrates that Mr. 

 Binney^s examples present the same type of organization 

 as the Calamitea described by linger. 



Dr. Dawson^ of Canada, detected in Calamodendron 

 some traces of what he terms " wood-cells, with one row of 

 large pores on each side"t- And in another part of his 

 paper he again refers to them as tissues in which " the 

 disks or pores are large and irregularly arranged, either in 

 one row or several rows/^ Of course neither of these 

 descriptions exactly agrees with the reticulated fibres of 

 my plant ; but as Dr. Dawson expressly associates his ex- 

 amples with the fibres seen in Dadoxylon, I conclude that 

 he may have met with a Calamodendron of a type ap- 

 proaching nearer to my plant than to those of M. Unger 

 and Mr. Binney. 



Dr. Dawson has further illustrated this subject in the 

 2nd edition of his ' Acadian Geology/ where he figured 



* Observations on the Structure of Fossil Plants found in the Carboni- 

 ferous Strata, by E. W. Binney, RR.S., F.G.S.— Part i. Calamites and Cala- 

 modendron. London, printed for the Palaeontographical Society, 1868. 



t " On the conditions of the deposition of Coal, more especially as ilhis- 

 trated by the Coal-measures of Nova Scotia and New Brunswick," Quarterly 

 Journal of the Geological Society, vol. xxii. 1866. 



