The ~FERTILISED OOSPHERE~ divides into an upper (hypobasal) and a lower (epibasal) cell; from the latter alone the embryo is developed with its root, stem, foot, and two _cotyledons_, and the former gives rise to an organ which appears in this instance for the first time, but which occurs in all Flowering-plants, viz. the _suspensor_. This forces the embryo down into the “endosperm,” which is entirely or partially absorbed by the embryo. In the case of the Flowering-plants the embryo is developed with its longitudinal axis in the elongation of the suspensor, but in _Selaginella_ the embryo is situated _transversely_ to it. _Selaginella_ (300–400 species), is essentially tropical, only one species living in the North (_S. spinulosa_), but others grow in Central and South Europe. Order 3. =Lepidodendraceæ= are extinct, tree-like Lycopods, which are found especially in the Lower and Middle Carboniferous. Vegetatively they are most nearly related to _Lycopodium_, but the stem attained much larger proportions (about eleven metres in height and one metre in thickness), and had a cambium by which it increased in thickness. It was regularly dichotomous, and closely studded with spirally-placed leaves, which left behind them peculiar rhombic scars. The large cones resemble Pine-cones, and bore sporangia much larger than any which are now produced (the male ones as much as 2 cm.’s in length). The macrosporangia were situated at the base, and the microsporangia at the apex. Order 4. =Sigillariaceæ.= These are, presumably, another group of extinct tree-like Lycopods (especially in the Middle Carboniferous). The name has been derived from the seal-like scars, which the fallen leaves have left behind in longitudinal rows on the grooved stem. The rhizomes of these plants were formerly termed _Stigmaria_, and placed in a separate genus. Order 5. =Sphenophyllaceæ= form an entirely extinct group. They do not definitely belong to any of the three large classes of Vascular Cryptogams, but it is perhaps best to place them in juxtaposition to these. They were herbaceous plants with verticillate, wedge-shaped leaves, with nerves branching dichotomously into equally strong branches. Micro-and macrosporangia were formed in the same cone; and were situated in the axils of the leaves, as in the Lycopods. The Transition from the Cryptogams to the Phanerogams.