Page:Proceedings of the Royal Society of London Vol 60.djvu/452

420 upturned foliaceous scale as well as a shorter and stouter downward prolongation.

Each of the fertile segments ends in a fleshy laminar enlargement not unlike the peltate scale of an or a These fertile laminae, which are protected on the exterior by the overlapping ends of the sterile segments, bear the sporangia. Pour, perhaps in some cases five, sporangia are attached, by their ends remote from the axis, to the inner surface of the peltate fertile lamina. Each sporangium is connected with the lamina by a somewhat narrow neck of tissue into which a vascular bundle enters. The sporangia are of great length, and extend back along the pedicels until they nearly or quite reach the axis.

The sterile and fertile segments alternate regularly, one above the other, in the same vertical series. So much is evident, but the question which segments are fertile and which sterile, has presented great difficulties, owing to the fact that the same segment can scarcely ever be traced continuously throughout the whole of its long course, and that the pedicels of sterile and fertile segments present no constant distinctive characters. For reasons, however, which will be fully given in a subsequent paper, I think it highly probable that in each sporophyll the segments of the lower lobe are sterile, and those of the upper lobe fertile, constituting the sporangiophores.

The sporangia and pedicels are all packed closely together so as to form a continuous mass. The external surface of the cone was completely protected by its double investiture of fertile and sterile laminae.

The spores are well preserved in various parts of the cone, and, so far as this specimen shows, are all of one kind, their average diameter being 0 065 mm. At the base of the cone, where macrospores, if they existed, might naturally be looked for, the spores are of the same size as elsewhere. So far, then, there is no evidence of heterospory. The spores are considerably larger than the microspores of the Lepidostrobi. Those of the Burntisland for example, are barely 0'02 mm. in diameter. The spores of our plant approach in size those of Sphenophyllum or the microspores of Calamostachys Casheana.

The sporangial wall, as preserved, is only one cell in thickness; it bears no resemblance to the palisade-like layer which forms the wall of the sporangium in Lepidostrbu, but has the same structure as that of a Calamostachys.* The sporangial wall of Sphenophyllum JDawsoni is similar.

The anatomy of the axis of the cone agrees closely with that of

and 5; Williamson and Scott, “ Further Observations on the Organisation of the Fossil Plants of the Coal-measures,” Part I, ‘ Phil. Trans.,’ 1894, PI. 81, fig. 31.
 * See Weiss, “ Steinkohlen-Calamarien,” vol. 2, 1884, Plate X XIV, figs. 3, 4,