840 



J. W. DAWSON ON A HPECIMKN OK DII'I.OXYLON 



lij»ncou3 liniiif?. liiive Ijocn of roiiHidcraMo firninoss, which would, in- 

 dfcd, Hocin to 1)0 iinplit'd in thu inaiiiKT of its jircstTViit ion within the 

 hollow bark. 



No traco remains of the tliick inner bark, which is represented by 

 Handstone ; and, us usual in these trees, the outer bark consista of 

 Hlruetureless coal. The outer surface of the sandstone cast shows lon- 

 gitudinal Htriution ; but the ribs, if presetit, arc very indistinct ; und 

 only a few sonu'what remote and indistinct depressions remain as 

 indications of the leaf-scars. The roots, as stated by Mr. ]lill, show 

 a delicate transverse wrinklin;;, which may be an cHect of pressure. 

 In oiw small jtortion only could 1 recognize on them the remains of 

 the stif^marioid areoles. 



When treated with an acid, the calcareous mutter is removed and 

 the wood renuiins as a crumblin<; dark brown mass, whioli shows the 

 structure very i)ertectly when diffused in water or Canada l)aLsam. 

 When this Itrown substance is if^nitcd it burns with scarcely any 

 tianu', and leaves a reddish ash, in which the bars of the scalariform 

 tissue are still (piite a]>i)arcnt. 



In sonu; jjiivts of the axis the medidlary cylinder becomes reduced 

 in size, and the inner scalariform cylinder proportionally thickentd. 

 Towards the top of the axis there is an indication of l)ifurcation, which 

 may, however, be a d'-ceptive appearance resulting from mechanical 

 splitting due to decay. 



The structures above described are obviously those of DIpIo.rijhm 

 of ('orda ; and the tree may be regarded as a Slijilhirin of this type, 

 the only well-characterized <me yet found in the Nova-Scotia coal- 

 field. In eoniijarison with the axes of Si<fillaria' which I have de- 

 scribed in fornuT papers presented to this Society, it agrees in the 

 general anaiigement of the tissues, but differs considerably in their 

 character. The pith cylinder is smaller and not Stcrnbergian. Tho 

 scalariform tissue of the inner woody cylinder and medidlary sheath 

 is nuu'h coarser. The outer cylinder, instead of ])seudo-8calariform 

 and porous tissue, like that of Cycads, has coarse scalarifonn ti8.sue. 

 In these respects the trunk resembles those recently described by 

 ^Villiamson*, aiul is also like specinuns from Arran shown to me 

 some years ago by Mr. C'arrutliers. From the examples given by 

 the fonner, 1 cannot doubt that such trees come within the limits of 

 the genus ISiffilhirla, as determined by tho ii. -.rkings of the bark ; 

 and that they belong to that low type of these trees in which tho 

 woody matter, while arrang( d in an exogenous manner, is wholly 

 scalariform, and with the nuduUary rays little developed. As Wil- 

 liamson has shown, these trees a]>]»r()ach closely to Liqiidixhwlra in 

 their structure. On the ctther hand, the tSitjillaritB of the type of 

 S. I'hyatis of l{r(mgniart, and of /S.NpinnlihSd of Renault and Grand'- 

 Kury, have a somewhat higher organization, and point to tho still 

 more elevated type descril)ed by me in 1M<>. There would thus 

 appear, as I pointed out in my paper on the structures of coal in 

 18.')1), and in that on the conditions of accumulation of coal in 1865, 



* 'ri!0)sii('tio!i<s (()■ tlie iliival Sociit}'. 



^ffiii'ihh^'i i 



