1876.] 



Fossil Plants of the Coal-measures. 



69 



Two kinds of sporangia of ferns are described. One of these has a 

 perfectly vertical annulus, such as is common amongst the Polypodiacese. 

 A second has a large, horizontal, subterminal annulus, approaching 

 closely to the form seen in the recent Grieicheniacese and SchizseaceaB, 

 especially resembling the latter type. Both these sporangia contained 

 spores ; in the first mentioned these were numerous and small ; in the 

 latter they are fewer in number, but of larger dimensions. The Grym- 

 nospermous stems of the Coal-measures are next examined. The small 

 branch of Dadoxylon from Coalbrook Dale, described by the author many 

 years ago in the Transactions of the Manchester Literary and Philo- 

 sophical Society, is first restudied. Its pith is Sternbergian ; its ligneous 

 zone has a medullary sheath of barred vessels, whilst its woody zone is com- 

 posed of wedges of discigerous fibres arranged exogenously and separated 

 by mural medullary rays. The disks of the fibres lack the central perfora- 

 tions seen in those of recent conifers. The bark is exactly like that of a 

 young shoot of a Taxus, consisting of an inner liber, the tissues of which 

 are arranged compactly in lines running parallel to each other and to the 

 surface of the wood ; whilst the outer layer consists of large parenchy- 

 matous cells, which in the living plant doubtless contained chlorophyl. 

 It appears to correspond to the phelloderm, no true phellein layer being 

 present. Other branches, especially from the G-anister beds near Oldham 

 and Halifax, are also described. Many of these are of much larger size, 

 but all have Sternbergian piths, with the exception of one in which the 

 parenchymatous medulla is not disciform, but like that of living conifers. 

 The chief peculiarity in the majority of these latter fossil branches and 

 twigs is that they give off small twin vascular bundles from the inner- 

 most surface of the ligneous cylinder. These pass outwards side by side 

 through the smaller branches, but can only be traced in the innermost 

 portions of the larger ones ; hence it is probable that they either supplied 

 leaves arranged in pairs (not distichously), or that they went to a 

 binerved leaf, the latter being most likely to have been their real des- 

 tination. The bark is rarely preserved in these larger specimens from 

 the Granister ironstones, in which they are associated with myriads of 

 Goniatites, an indication that they have been drifted from a distance and 

 long exposed to water — conditions very different from those charac- 

 terizing the origin of the coal in which most of the Oldham plants 

 have been obtained. 



The author discusses the claim set up by M. Brongniart and Professor 

 Newberry for the admission of SigiUaria amongst the Gymnospermous 

 exogens, as well as Dr. Dawson's opinion that some of them, at least, have 

 decided G-ymnospermous affinities ; but still believes that this determina- 

 tion is not justified by the facts. All the additional observations which he 

 has made since the publication of his second and third memoirs confirm 

 bis original conclusion that no true distinction can be demonstrated to 

 exist between the Sigillarice and the higher forms of Lepidodendra, in 



