DISTINCTION BETWEEN CORDAITES AND DADOXYLON. 531 



fallibly ascertained. For this reason it often happens that the same wood 

 in different states receives different names, and that the woods of different 

 species are confounded under one name. As an example of the latter case, 

 while it seems certain that the wood properly called Dadoxylon has belonged 

 to Walchia, yet there are two or three species of Walchia in the upper 

 Carboniferous of Nova Scotia and Prince Edward island, and I have not 

 been able, after examining great numbers of slices, to ascertain a similar 

 specific distinction in the woods showing structure. 



Mr. Howley's collection also contains a small stem, about two inches in 

 diameter, showing a very distinct radiating woody structure, with indications 

 of a pith destroyed by decay and compression. The wood of this specimen 

 is more thin-walled than the former, with short and unequal medullary rays 

 and the bordered pores less constant and continuous. These characters ally 

 it with the wood of Cordaites, which I believe can always, when well pre- 

 served, be distinguished from that of Dadoxylon. Leaves of Cordaites 

 horassifolia also occur in the collection. 



Another remarkable specimen is a quantity of loose and soft fibrous car- 

 bonaceous material resembling the mineral charcoal of coal. It contains a 

 small amount of calcareous matter, but not enough to give it coherence, and 

 can be studied only after treatment with nitric acid, when it presents de- 

 tached carbonaceous fibers. These show two to three rows of bordered 

 pores and traces of the medullary rays, and I imagine it must have been a 

 wood similar to the Cordaioxylon mentioned in the last paragraph. Material 

 of this kind, as I have elsewhere shown,* constitutes much of the mineral 

 charcoal of our coals. 



Still another specimen, from Codroy river, presented to me some years 

 ago by Dr. Robert Bell, is a black chert, which when sliced proves to be a 

 limpid quartz filled with shreds of vegetable matter. It is, in short, a con- 

 geries of fragments of herbaceous plants, appearing as if chopped up finely 

 or disintegrated by maceration, and imbedded in a clear silicious paste. 

 The tissues observed are scalariform vessels, delicate fibers and elongated 

 cells, and parenchymatous cellular tissue, with occasional remains of spore- 

 cases or macrospores. The mass may be characterized as a silicified vege- 

 table mould composed of fragments of the more delicate tissues not usually 

 preserved. In this it resembles some of the specimens found by Mr. Grieve 

 under the trappean beds of Burntisland, in Scotland, which have been de- 

 scribed by Professor Williamson. I hope to make further examination of this 

 material, and in the meantime would direct attention to it as possibly afford- 

 ing, in some parts of it, more complete organs of plants than those in the 

 specimens in my possession. 



* Quart. Journ. Geol. Soc, vol. XV, 1859, p. G26. 



