Each sporophyll, attached almost at right angles to the cone-axis, bears a radially elongated sporangium seated on the median line of its upper face; its margins are laterally expanded as a thin lamina; from the middle of the lower face a narrow keel extends downwards between two sporangia belonging to a lower series. From the base of a sporangium a mass of sterile tissue penetrates into the spore-producing region as in the large sporangia of _Isoetes_ (cf. fig. 191, H, _a_, and fig. 133, H). The distal and free portion of the sporophylls is bent upwards as a protecting bract. Some of the sporangia in the upper part of the cone produced numerous microspores, while 8–16 megaspores occur in the lower sporangia. The megaspores, having a mean diameter of 0·8 mm. “quite 40 times the size of the microspores[380],” are characterised by tubular capitate appendages, and by a conspicuous three-lobed projection (fig. 191, E)[381] which, as Scott suggests, may represent the outer spore-wall which has split as the result of germination. It is not improbable, as shown in fig. 191, I, that this cap was present before germination. The megaspores represented in fig. 191, I, illustrate their characteristic form as seen in a section of a megasporangium, _Sm_; the open beak-like portion of the larger spore is probably the apical region which has split along the three-rayed lines. These lines form a characteristic feature of both recent and extinct spores and denote their origin in tetrads. The spore shown in fig. 191, E[382], illustrates the external features. The apical region of the prothallus of a megaspore of _Lepidodendron Veltheimianum_ described by Mr Gordon[383] consists of smaller cells than those occupying the greater part of the spore-cavity, a differentiation which he compares with that of the prothallus of _Selaginella_. [Illustration: FIG. 186. A, B. _Lepidodendron Veltheimianum._ (Botany School, Cambridge.) C. _Lepidodendron macrophyllum._ (British Museum. No. 377.) _x_, Primary xylem; _x_², secondary xylem; _s_, Stigmarian rootlet.]