epidermis remains: there is a definite megaspore-membrane surrounding the prothallus-tissue in which there were probably two archegonia (fig. 494, A, _a_)[889]. The nucellus stands free within the integument from which it is separated by a space (_s_, fig. 494, A). Microspores are frequently met with in the pollen-chamber in which they matured after their introduction through the micropyle, probably with the aid of a drop of mucilage: they are large oval bodies with an average size of 160μ × 100μ, some reaching over 200μ, in length and, as Renault was the first to point out, within a finely granulate exospore there are several thin-walled cells: this statement was not accepted by some authors but Prof. Oliver’s researches have amply confirmed it, and an examination of the original preparations convinced me that Renault had correctly described the structural features. Oliver shows that there are about 20 cells within each microspore regularly arranged as rows of five wedge-shaped elements with their pointed ends directed towards the centre, and he thinks that these cells may have undergone further division to produce sperm-mother-cells, though there is not such good evidence of this as in the differently constituted microspores of _Stephanospermum caryoides_. No trace of pollen-tubes was found and it is probable that the antherozoids were liberated by the rupture of the delicate prothallus-tissue. The tracheal sheath afforded an adequate means of water-supply to the pollen-chamber and this enabled the motile antherozoids to reach the archegonia. _Stephanospermum caryoides_ Oliver[890]. This species, founded on a specimen from ., is a larger seed (15·5 × 12·5 mm.) and more globular than _S. akenioides_; there is a shorter micropylar beak and a less developed peri-micropylar trough. As in _S. akenioides_ the nucellus is free from the base and the two species conform to the same general type of construction. The microspores are distinguished by the presence of only two internal cells which do not occupy the whole of the spore-cavity but are surrounded by a large peripheral cell comparable with the tube-cell in recent microspores, though there is no proof that a tube was formed: in the case of _S. akenioides_ Oliver considers that fertilisation was not assisted by the production of a pollen-tube. The two cells by further division gave rise to a secondary cell-complex consisting of at least eight antherozoid-mother-cells. No antherozoids have been found in the microspores but it is possible that two small bodies, 17μ × 15μ, met with in a pollen-chamber may represent the nuclei of sperms. Their small size differentiates them from the much larger male gametes of Cycads and from the supposed sperms of _Physostoma_ and _Lagenostoma_.