Lycopodiaceae P.Beauv.

Terrestrial, epiphytic, scrambling or climbing plants of varied habit; either with indeterminate, horizontal and subterranean, creeping, looping or climbing stems, giving rise to determinate, erect or inclined, simple or branched, aerial stems, usually of different thickness to the horizontal stems; or with erect or pendent, dichotomously branched stems of equal thickness, lacking horizontal indeterminate stems; very rarely with a simple stem and a cluster of leaves growing from a subterranean tuber.  Scales absent. Roots either arising at varying intervals along the length of horizontal stems, or forming a single basal tuft on erect or pendent species. Leaves appearing to be spirally arranged, or regularly or irregularly whorled, or in longitudinal ranks, lacking a ligule, undivided, with a single unbranched vein; all similar or sometimes gradually reducing towards the apex, or rarely of two kinds and arranged in ranks (anisophyllous); leaf margins entire or minutely ciliate. Bulbils rarely present on aerial stems, or usually absent. Sporophylls similar to the leaves, or modified and aggregated into distinct strobili, persistent or ephemeral, monomorphic. Strobili usually terminal on ultimate branches or rarely lateral on overtopping branches, erect or pendent, sessile or stalked. Sporangia solitary, in axils or on adaxial surface of sporophylls, monomorphic, homosporous. Spores trilete, cream or yellow, foveolate, rugulate, reticulate and baculate (NZ), or scabrate (not NZ).

A family with five genera (Burnard et al. 2016) and c. 388 species (PPG 1 2016).

Lycopodiaceae have long been recognised as one of three isolated families within the Lycopodiopsida, distinguished by their terrestrial, epiphytic or climbing/scrambling habit, non-ligulate leaves, and homosporous sporangia, usually borne in strobili. Subdivision of the family has been subject to considerable disagreement, with anything from two to 16 genera having been recognised. Traditionally the monotypic Phylloglossum was accepted alongside the large genus Lycopodium, which was the classification used by Allan (1961) for New Zealand species. However, a detailed investigation of the family led Øllgaard (1987, 1989, 1990) to recognise four genera: Huperzia, Lycopodiella, Lycopodium and Phylloglossum, with four sections in Lycopodiella and nine in Lycopodium. In doing so, he rejected the much more divisive classifications of Rothmaler (1944) and Holub (1964, 1975, 1983, 1985, 1991), who recognised two families (Huperziaceae and Lycopodiaceae) and subdivided Huperzia into two genera, Lycopodiella into four, and Lycopodium  into seven. PPG 1 (2016) has accepted the more divisive approach and extended the subdivision of Lycopodium to nine genera, with a total of 16 in the whole family. Molecular analysis of Lycopodiaceae based on four chloroplast loci in 119 taxa (Field et al. 2016) demonstrated that both the broader classifications of Øllgaard and the divisive scheme of PPG 1 are monophyletic, leaving it a matter of interpretation as to which should be accepted.

Field et al. (2016) showed that, within the huperzioid clade, there is a clear choice between accepting one genus (Huperzia) or three (Huperzia, Phlegmariurus and Phylloglossum). There are good morphological and geographical grounds for recognising three genera (discussed below under each genus), and hence they are accepted here. Within the lycopodioid clade there is strong morphological and molecular evidence for distinguishing Lycopodiella and Lycopodium, but the evidence for subdividing them is less compelling. A monophyletic arrangement requires recognition of either two genera with about 50 species in each, or 13 small genera, of which three are monotypic and four have five species or less (PPG 1 2016). Morphological support for these smaller genera is weak, or depends on obscure characters, and only the two broader genera are accepted here.  Furthermore, our approach minimises differences from schemes used recently in New Zealand.

Lycopodiaceae comprise terrestrial, epiphytic or climbing/scrambling lycophytes bearing non-ligulate leaves, which are either monomorphic or dimorphic with single, unbranched veins. Sporangia are homosporous, solitary in the axils or on the adaxial surface of the sporophylls, and usually aggregated into strobili. In huperzioid lycophytes the branching is isotomous, with all dichotomies resulting in equally thick branches, and the roots form a basal tuft. In lycopodioid plants the branching is anisotomous, with indeterminate horizontal main stems and determinate aerial branch systems, and the roots arise along the lower side of the main stems.

The anatomy and morphological variability of New Zealand species of Lycopodiaceae were studied in detail by Holloway (1910, 1919), along with observations on methods of vegetative reproduction (Holloway 1917) and investigations of their life cycles and gametophyte generations (Holloway 1916, 1920). The spores of all New Zealand species were described and illustrated by Large & Braggins (1991).