PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
222 
still regard as the nearest relatives of the modern Conifers that the Coal-measures have 
yet furnished. 
In September, 1851, I laid before the Literary and Philosophical Society of Man- 
chester a memoir “ On the Structure and Affinities of the Plants hitherto known as 
SternbergiceP Dr. Dawson, of Montreal, had previously shown* * that some fragments, 
of wood “ much resembling the wood of the Coniferse ” had internal “ stony casts having 
irregular and often large transverse markings.” In my memoir referred to I arrived at 
the conclusion that all the Sternbergian specimens hitherto found in our British Car- 
boniferous deposits w r ere casts of the internal pith-cavities of stems and branches 
belonging to Endlicher’s genus Dadoxylon, a conclusion which more than twenty 
years of further research has thoroughly confirmed. Corda, in his classic volume, had 
previously figured and described, under the name of Lomatophloios crassicaule, a 
Lepidodendroid plant with a Sternbergian pith-cavity, and Dr. Dawson believes that a 
similar pith is characteristic of some Sigillarian stems which he has discovered in the 
Coal-measures of the Dominion ; but British observers have hitherto failed to detect 
any similar Lepidodendroid or Sigillarian forms in our Coal-measures. I repeat that 
every fragment of Sternbergia hitherto found in our Islands, the surrounding tissues of 
which show satisfactory indications of structure, belongs to the genus Dadoxylon. 
In 1849 M. Brongniart published, in the ‘ Dictionnaire Universel d’Histoire Natu- 
relle,’ his very important “ Tableau des genres de Yegetaux Fossiles.” On comparing 
his views as enunciated in this memoir with those embodied in his earlier ‘ Prodrome,’ 
we find that they underwent a vast change, so far as the question of Carboniferous 
Gymnosperms is concerned. In his later publication he included in that group Calamo- 
dendron , Asterojphyllites, Sphenojohyllum, Annularia , the entire group of Sigillarice with 
their Stigmarian roots, the Diploxylons of Corda, the Medullosce of Cotta, and a number 
of other less important plants. It is not necessary to say that I altogether reject these 
arrangements. I have, in previous memoirs of this series, given my reasons for believing 
that the Calamodendra are all Equisetacean, that Sigillaria and Diploxylon are Lepido- 
dendroid, that Aster opdiyllites and Sjohenojohyttum, if not Lycopodiaceous, cannot possibly 
be regarded as Gymnospermous, and that Medullosa is certainly a Marattiaceous Fern. 
But M. Brongniart also included in that Gymnospermous group several of the recently 
established genera of Carboniferous plants, such as the Pinites medullaris and the 
P. Withami of Lindley and Hutton, which he placed in his genus Palceoxylon. In 
like manner he placed the Pinites Prandlingi in Endlicher’s genus Dadoxylon , and the 
Pitus primasva and P. antiqua of Witham in Endlicher’s genus Pissadendron. These 
and other supposed fossil coniferous woods Brongniart threw into two groups according 
organization of the walls of the woody tissue of recent Coniferae does not exist in this fossil, but is supplied by 
another kind of structure of an equally unusual nature, the inference that this tree belonged to the coniferous 
tribe cannot he considered altogether just.” — Loc. cit. p. 12. 
* Proceedings of the Geol. Soc. London, No. 6, Jan. 1846. 
