272 



HARD WICKE'S SCIENCE- GOSSIP, 



tree-like forms that the student readily learns to distin- 

 guish them from the other fossil plants. In several 

 places they have been found with their original 

 woody structure well preserved, and microscoj)ic 

 sections taken from them have fully demonstrated the 

 fact, that these plants belonged to the pine family, 

 and that their nearest modern representative is the 

 Araucaria or Norfolk Island pine. These fossil 

 pines are known by the name of Dadoxylon. The 

 great majority of fossil plants appear to have 

 grown on large plains or mud flats, which were 

 but little elevated above the sea level, where they 

 seem to have grown most luxuriantly and formed 

 those extensive vegetable deposits which ultimately 

 became converted into coal. But the Dadoxylons 

 appear to have preferred a different habitat, and to 



F'S- ISO- — Stcritlcrgia (natural size), from specimen in ^ 

 Author's collection. 



have grown in the more elevated districts of the 

 Carboniferous lands, and this preference for upland 

 districts appears to have characterised the pine tribe, 

 m every succeeding geological age down to the 

 present day. Storms and hurricanes also ajjpear to 

 have occasionally prevailed among the ancient 

 Dadoxylon forests, causing death and destruction 

 among them, and scattering their fragments far and 

 wide, and these along with the uprooted stems were 

 sometimes carried by floods into the rivers and 

 deposited in the sandbanks at the mouths of the 

 rivers, where many of them became fossilised and 

 ultimately, after the lapse of untold ages, arc now being 

 exposed to the light of day by quarrying operations. 

 The same sandbanks would also receive the wreck 

 from the lower levels inhabited by the chief coal form- 



ing plants, and hence we frequently find the remains of 

 Dadoxylon side by side with those of Lepidodendron,^ 

 Sigillaria, &c. Although Dadoxylon and Sternbergia 

 are nearly always found associated together in the 

 same sandstone quarries, yet their relationship 

 was not suspected, until Professor Williamson clearly 

 demonstrated the fact that Sternbergia was merely a 

 cast of the pith of Dadoxylon. Some years ago 

 he obtained a specimen of a fossil plant from Coal- 

 brookdale which proved to be part of the stem of a 

 Dadoxylon, It was a few inches in length by a little 

 over half an inch in diameter, and was enclosed in a 

 calcareous nodule. It was in a wonderfully good 

 state of preservation, showing to perfection the 

 various tissues composing the bark, woody cylinder, 

 and the cellular pith. The structure of the bark and 

 woody cylinder showed that the plant was a fossil 

 pine, while the exposed pith showed the transverse 

 bars of Sternbergia. Thus, these two fossils, which 

 had up to that time been regarded as belonging to 

 widely different species, were found to belong to one 

 and the same species. What kind of a plant Sternbergia 

 had been, was always a difiicult problem to solve, and 

 in fact never had been solved, until its true nature was 

 seen in this unique specimen. Some of the recent pines 

 have a moderately large pith of very deUcate cellular 

 tissue, and the ancient Dadoxylons had even larger and 

 quite as delicate piths. In some of my specimens o^ 

 these fossil pines the diameter is nearly equal to half of 

 that of the stem. In smaller specimens the proportion 

 is not so great. Upon the death of the plant, the pith 

 seems to have been the first to decay, and when it 

 became imbedded in sand or other material, its- 

 hollow centre became filled by the infiltration of sand 

 or lime, or other surrounding material. In this 

 manner a solid core was formed, which was in many 

 instances an exact model of the original pith, and 

 retaining its external markings. Both the surround- 

 ing ligneous zone and bark might afterwards be 

 completely destroyed, as appears to have been the- 

 case when we find isolated portions of Sternbergia 

 in sandstone rocks, or the woody cylinder and pith 

 might both have been destroyed and the bark alone 

 preserved until a solid core of sandstone had been 

 formed, and then there would remain the tree-like 

 form of an ordinary Dadoxylon enveloped in its 

 filmy layer of dark carbonaceous matter, which is the 

 mineralised remains of the original bark. I, have 

 found specimens of Dadoxylon in all the geological 

 formations in the neighbourhood of Halifax, includ- 

 ing the coal-measures, millstone grit and Yoredale 

 rocks. In the beds of shale, in all the three formations, 

 tiiere occur calcareous nodules, which contain the 

 remains of marine shells, such as Goniatites, Nautili, 

 Orthoceras, &c., and fish remains; they also, not 

 unfrequently, contain fragments of Dadoxylon which 

 have the structure well preserved. One of the best 

 specimens in my cabinet came from the Yoredale 

 rocks of Ilebden Bridge, but I have obtained some 



