In 1877 Williamson described some detached petrified seeds from the Lower Carboniferous rocks of Fifeshire, Scotland, as _Conostoma ovale_ and _C. intermedium_. Dr Benson’s investigation[222] of these two forms leads her to confirm Williamson’s doubts as to the validity of a specific separation and she assigns the single type to the new genus _Sphaerostoma_. The seeds are always associated with the vegetative organs of _Heterangium Grievii_. In 1909 Oliver[223] expressed the opinion that the Burntisland species of _Conostoma_ (= _Sphaerostoma_) is probably the seed of _Heterangium_. The seed consists of a central body representing the nucellus, an inner integument, and an enveloping cupule or outer integument: most specimens have lost the cupule and in this condition they are 3·5 mm. long with a maximum breadth of 2·2 mm. In the middle the seed is circular in transverse section and octagonal near the base and apex. The free apical part of the integument forms a frill (canopy) round the micropyle and extends beyond the nucellar apex which consists of a relatively flat plinth surmounted by a central dome or lagenostome (fig. 414). The lagenostome is surrounded by an annular pollen-chamber on to the lower surface of which abuts the large embryo-sac, and remains of archegonia were noticed below the pollen-chamber. The roof of the chamber in the young state consists of a layer of thin-walled cells extending across the flattened apex of the nucellus, _n_, but as the pollen-chamber becomes differentiated from the nucellar tissue by the disorganisation of the zone of cells its roof-cells thicken their vertical walls and assume the structure of a multiseriate annulus, which acts as a mechanism for opening the pollen-chamber by a circular dehiscence in such a way that the edge of the ruptured roof of the pollen-chamber slightly overlaps the periphery of the central column of nucellar tissue after it has returned to its original position subsequent to the entrance of the microspores. The micropylar region is surrounded by eight lobes of the integument and each is characterised by a crest of radially elongated cells, fig. 414, _f_, especially prominent on the outer side. External to this is the slightly longer cupular sheath (fig. 414, _c_) which may also have been lobed. The surface of the integument below the terminal crests consists of a layer of cells with small papillae which eventually ruptured and discharged mucilage. Both integuments have a vascular supply, that of the inner integument being represented by eight vascular bundles, some of which were found to have mesarch xylem, given off from the single strand in the pedicel. Fig. 414 shows the apical region of a seed of _Sphaerostoma_: the flat-topped nucellar cap, _n_, is surrounded by the annular pollen-chamber, _pc_, below which are indicated the archegonia: the wall of the megaspore (embryo-sac) is seen at _m_ and external to this vascular bundles, _v_, run up the inner portion of