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X. On the Organization of the Fossil Plants of the Coal-measures . — Part IV. 
Dictyoxylon, Lyginodendron, and Heterangium. Jig W. C. Williamson, F.P.S., 
Professor of Natural History in Owens College , Manchester. 
Received December 4, 1S72, — Read December 19, 1872. 
On February 20th, 1866, Mr. Binney gave to the Literary and Philosophical Society 
of Manchester a brief description of a new plant from the Lower Carboniferous beds of 
the neighbourhood of Oldham. The following extracts from the ‘ Proceedings ’ of the 
Society embody some of the chief points of that description. 
“ It evidently belonged to the genus Pinites of Witham, since changed by Endlichee 
and Beongniaet into Padoxylon .” It “ has a medullary axis composed of irregular 
polygonal cells separated by intervening spaces vertically, and thus forming a kind of 
discoid pith.” “ This is separated from lunette-shaped bundles of hexagonal tubes 
arranged in a convex form from the pith inwards, and lessening in size as they pass 
outwards into wedge-shaped masses of four-sided subhexagonal cellules arranged in 
radiating series, and divided by large medullary rays or bundles, which appear to 
originate in the lunette-shaped masses. On the outside of this internal radiating 
cylinder are other lunette-shaped bundles similar to those in the inside.” “ Then comes 
a narrow zone of lax tissue, which has been a good deal disarranged. Outside this are 
some thin wedge-shaped bundles of cellules full of dark carbonaceous matter, and 
arranged in radiating series of varying sizes, separated by lax tissue, probably represent- 
ing the bark of the tree.” 
“ In the longitudinal section the cellules are seen to he greatly elongated and divided 
with oblique and transverse dissepiments placed at great distances. Two of the walls, 
viz. those facing the medullary rays, are regularly reticulated with six, seven, and eight 
series of hexagonal areolae arranged regularly but not in a line.” 
“ In the tangential section the walls of the cellules also show a reticulated appearance, 
something like that previously noticed, but not in so marked and distinct a manner ; and 
the medullary rays or bundles, in their section, show numerous irregular series of small 
cellules of one to four, and more rarely much larger cellules.” 
“ The areokc on the walls of the cellules are more numerous than in any species of 
Pinites or Padoxylon that have hitherto come under my notice, the Pinites medullaris 
of Witiiam having the walls of its elongated cellules with two, three, and four series of 
contiguous areolae, and those only on the walls parallel to the medullary rays, whilst in 
my specimen they are reticulated with six, seven, or eight, and not only on such walls, 
but also on the walls at right angles to the medullary rays.” 
MDCCCLXX1II. 3 E 
