88G Rcvietvs — Dawson's Acadian Geology. 



these so-called medullary rays to the vascular axis and to the sepa- 

 rate internal vascular bundles, together with the entire absence of 

 any indication of the cellular structure of the medullary ray in radial 

 sections, put it, in our estimation, beyond a doubt that they cannot 

 be considered as medullary rays. We have never met with a speci- 

 men of Sigillaria in which the woody cylinder was preserved, but 

 we have examined a large series of Stigmarim in which the vascular 

 tissue was in a good state of preservation. The vascular axis of 

 Stigmaria is certainly composed entirely of scalariform vessels, per- 

 fectly free from medullary rays, but traveled in an upward and out- 

 ward direction by vascular bundles which pass from the interior of 

 the c^dinder through the meshes made by the opening and closing of 

 the vascular tissue.^ So far this agrees with what was observed and 

 figured by Brongniart in the stem of Sigillaria elegans, with Binney's 

 Sigillaria vascularis, with Lindley and Hutton's Lepidodendron Har- 

 courtii, and with several specimens of Lepidodendron which we have 

 examined. If true disc-bearing gymnospermatous tissue has been 

 found in situ forming an outer layer surrounding the scalariform 

 tissue, the notions hitherto entertained regarding the systematic 

 position of this genus deduced from the structure of the stem will 

 be greatly modified. But its absence in those exquisitely preserved 

 stems of which drawings and descriptions have been published, as 

 well as in Stigmaria, the undoubted roots of Sigillaria, makes us 

 hesitate to refer such tissue found in coal to this genus, and set aside 

 any argument based upon this to place Sigillaria as high in the 

 vegetable kingdom as the Gymnosperms. No argument can be built 

 upon the supposed fruits of Sigillaria, for, as yet, no one has found 

 them so related as to make their connection probable. 



The only Gymnosperm in Principal Dawson's list is, we believe, 

 the genus Dadoxylon, and it is worthy of remark that if complexity 

 in the structure of the medullary ray be any indication of higher 

 organisation, then these Palaeozoic conifers were more highly or- 

 ganised than any that have followed them. 



To conclude, the evidence before us is greatly in favour of reduc- 

 ing Sigillaria from the Gymnosperms to the neighbourhood of 

 Lepidodendron among the vascular cryptogams, and of placing 

 Megaphyton beside them rather than among the ferns, and of reduc- 

 ing also Calamodendron and uniting it with Catamites as a genus of 

 Equisetacece. 



While difiering in these respects from the conclusions of Dr. 

 Dawson, it requires only a glance at the work by a student of these 

 ancient forms of vegetable life to perceive that there is here one of 

 the most important of modern contributions to the science of 

 palseontological botany. W. Carruthers. 



* "We write this remembering that Cotta has figured a longitudinal section of 

 Utigmaria Jicoides^ the vascular tissue of which is composed of Cycadean-like vessels 

 traversed by the muriform cells of medullary rays, but it is quite certain that if this 

 is a faithful representation of the wood of the fossil, the fossil is not Sligmaria 

 ficoides. 



