The species _Conostoma anglo-germanicum_ agrees closely with _C. oblongum_ in general form and organisation, but it has eight ribs, four more prominent than the others, and differs also in other minor characters from the rather shorter seeds of the type-species. _Conostoma_ differs from _Lagenostoma_ in the absence of the tubular prolongation of the lagenostome, the micropyle being like that in recent Gymnosperms. In _Conostoma_ the tracheid-like elements of the lateral wall of the lagenostome are a characteristic feature, and no evidence has been found of the existence of a central core of tissue such as occupies the centre of the seed-apex in _Lagenostoma_. The long hairs of _Physostoma_ are represented in _Conostoma_ by the much smaller mucilaginous cells of the epidermis and in _Lagenostoma_ by the less closely united mucilage-cells of the superficial layer of the testa. =Sphaerostoma.= Benson. As already pointed out in Chapter +xxix.+ where this genus is described as probably the seed of _Heterangium_, there is a fairly close general resemblance between _Sphaerostoma_ and _Lagenostoma_. In the presence of free apical lobes the former genus resembles _Conostoma_, and while agreeing with _Lagenostoma_ in its annular pollen-chamber it is peculiar in the retention of an epidermis over the roof of the pollen-chamber: as in _Lagenostoma_ the seed is enclosed by an outer integument or cupule. =Lagenostoma.= Williamson. An account of this type of seed is included in the description of _Lyginopteris_[837]. The more striking peculiarities are exhibited by the pollen-chamber and the free region of the integument: the annular pollen-chamber (fig. 493, D, _c_; fig. 409) surrounds a central nucellar cone and is prolonged upwards as a tube engaging with the micropyle in contrast to the form of the pollen-chamber and the absence of a tubular prolongation in _Conostoma_. The tentacles of _Physostoma_ and the short apical lobes of _Conostoma_ are replaced by an apical cone formed by the coalescence of the integument containing nine cavities originally filled with parenchyma (figs. 409; 493, B). The presence of a cupule is a characteristic feature of young seeds, but from negative evidence in the case of most other seeds it is unsafe to assume that the cupule of _Lagenostoma_ is an exceptional feature. The nucellus and testa are united as far as the shoulders of the seed as in the seeds of recent Cycads and in contrast to their lateral independence in _Trigonocarpus_, _Stephanospermum_, and other genera. =Gnetopsis.= Renault.