The recent members of the Lycopodiales are considered apart from the extinct genera in order that our examination of the latter may be facilitated by a knowledge of the salient characteristics of the surviving types of this important section of the Pteridophyta. A general acquaintance with the extinct as well as with the recent genera will enable us to appreciate the contrasts between the living and the fossil forms and to realise the prominent position occupied by this group in the Palaeozoic period, a position in striking contrast to the part played by the diminutive survivors in the vegetation of the present day. In the account of the recent genera special attention is drawn to such features as afford a clue to the interpretation of the fossils, and the point of view adopted, which at times may appear to lead to an excessive attention to details, is necessarily somewhat different from that represented in botanical text-books[83]. A. =HOMOSPOREAE.= =Lycopodiaceae=: genera _Phylloglossum_, _Lycopodium_. B. =HETEROSPOREAE.= =Selaginellaceae=: genus _Selaginella_. =Isoetaceae=: genus _Isoetes_. The existing plants included in the Lycopodiales are in nearly all cases perennial herbaceous pteridophytes, exhibiting in their life-histories a well marked alternation of generations. The sporophyte (asexual generation) is characterised by the relatively small size of the leaves except in the genus _Isoetes_ (fig. 132) and in the Australian and New Zealand genus _Phylloglossum_. The stems are usually erect or trailing, pendulous in epiphytic species or small and tuberous in _Isoetes_ and _Phylloglossum_. The repeated forking of the shoots (monopodial and dichotomous branching) is a prominent feature of the group. The vascular tissue of the stem usually assumes the form of a single axial strand (stele) (fig. 125), but the shoots of some species of _Selaginella_ often contain two or more distinct steles (fig. 131). The group as a whole is characterised by the centripetal development of the xylem composed almost entirely of scalariform tracheids: secondary xylem and phloem of a peculiar type occur in _Isoetes_, and the production of secondary xylem elements in a very slight degree has been noticed in one species of _Selaginella_ (_S. spinosa_)[84]. The roots are constructed on a simple plan, having in most cases only one strand of spiral protoxylem elements (monarch structure). In _Lycopodium_, in which stem and root anatomy are more nearly of the same type than in the majority of plants, several protoxylem strands may be present. The sporangia are axillary or, more frequently, borne on the upper surface of sporophylls, which are either identical with or more or less distinct from the foliage leaves; in the latter case the sporophylls often occur in the form of a well defined strobilus (cone) at the tips of branches.