To supply the vascular tissues of the leaf traces, simple strands come off from the outer part of the primary wood, where groups of small-celled protoxylem project (see _px_ in fig. 97). The leaf strands _lt_ move out through the cortex in considerable numbers to supply the many leaves, into each of which a single one enters. [Illustration: Fig. 97.—Transverse Section of Outer Part of Primary Wood of _Lepidodendron_, showing _px_, projecting protoxylem groups; _lt_, leaf trace coming from the stele and passing (as _lt_^1) through the cortex] As regards the fructifications of _Lepidodendron_ much could be said were there space. The many genera of _Lepidodendron_ bore several distinct types of cones of different degrees of complexity. In several of the genera the cones were simple in organization, directly comparable with those of the living Lycopods, though on a much larger scale (see p. 67). In some the spores were uniform, all developing equally in numerous tetrads. The sporophyll was radially extended, and along it the large sausage-shaped sporangia were attached (see fig. 98). The tips of the sporophylls overlapped and afforded protection to the sporangia. The axis of the cone had a central stele with wood elements like those in the stem. The appearance of a transverse section of an actual cone is shown in fig. 99. Here the sporangia are irregular in shape, owing to their contraction after ripeness and during fossilization. Other cones had sporangia similar in size and shape, but which produced spores of two kinds, large ones resulting from the ripening of only two or three tetrads in the lower sporangia, and numerous small ones in the sporangia above. [Illustration: Fig. 98.—Longitudinal Diagram, showing the arrangement of the elongated sporangia on the sporophylls _a_, Main axis, round which the sporophylls are inserted; S, sporangium; _s_, leaflike end of sporophyll.] The similarity between the _Lepidodendron_ and the modern Lycopod cone has been pointed out already (p. 67), and it is this which forms the principal guarantee that they belong to the same family, though the size and wood development of the palæozoic and the modern plants differ so greatly. The large group of the Lepidodendra included some members whose fructifications had advanced so far beyond the simple sporangial cones described above as to approach very closely to seeds in their construction. This type was described on p. 75, fig. 54, in a series of female fructifications, so that its essential structure need not be recapitulated. [Illustration: Fig. 99.—Transverse Section through Cone of _Lepidodendron_ A, Main axis with woody tissue; _st_, stalks of sporophylls cut in oblique longitudinal direction; _s_, tips of sporophylls cut across; S, sporangia with a few groups of spores. (Microphoto.)]