He summarises what was known at that time as to the structure of the ovule, acutely criticising the views of the various authors he cites. He emphasises the need of studying the _development_ in order successfully to interpret the mature structure. He insists on the origin of the seed coats from the integuments, on the orientation of the embryo within the amnios (embryo sac), and on the distinction between the true albumen which is contained in this "amnios" and the albumen "formed by a deposition of granular matter in the cells of the nucleus" (nucellus), i.e. the perisperm, and he goes on to suggest that in some of these cases the "Membrane of the amnios seems to be persistent, forming even in the ripe seed a proper coat for the embryo.... This is the probable explanation of the structure of true Nympheaceae" ... here he seems to have overlooked the rudimentary endosperm which is really present. Finally he sums up an admirable account of the whole matter as follows:--"The albumen, properly so-called, may be formed either by a disposition or secretion of granular matter in the utriculi of the amnios, or in those of the nucleus itself, or lastly that two substances having these distinct origins and very different textures may coexist in the ripe seed as is probably the case in Scitamineae." He then goes on at once to argue that the apex of the nucleus is the point of the ovulum where impregnation takes place, and adds that "all doubt would be removed if cases could be produced where the ovarium was either altogether wanting or so imperfectly formed that the ovulum itself became directly exposed to the action of the pollen or its fovilla." This leads him at once to enunciate his view of the gymnospermy of Cycads, Conifers and Gnetaceae. He reviews very fully the opinions that had been expressed by others as to the real structure of the female organ, especially of Pinus, and he mentions the fact that he himself in the botany of the Flinders' voyage had previously held the view that a minute perianth was present in the Pine, a view which, as he says, "On reconsidering the subject in connection with what I had ascertained respecting the vegetable ovulum" he had now abandoned.