Dendrolycopodium A. Haines. Groundpine, Tree-clubmoss.
A genus of 4 species, temperate and subarctic. Haines (2003a) made the case for this genus as distinct from Lycopodium s.s. and other relatives. Later phylogenetic studies have corroborated this decision (e.g., Testo, Field, & Barrington 2018).
ID notes: Dendrolycopodium is similar in overall appearance to Diphasiastrum. Both genera have horizontal rhizomes (on or below the ground surface), bearing vertical stems at intervals, and each vertical stem bears sterile branchlets and fertile branchlets. The sterile branchlets are horizontal to ascending, and branch dichotomously (in Ys), while the fertile branchlets are erect and terminate in narrow strobili (cone-like structures) which bear the sporangia. At all seasons, Dendrolycopodium is easily distinguished from Diphasiastrum by its leaves, which are needle-like (but only slightly stiff), and which spread away from the branches at acute to right angles, giving the plant a slightly prickly appearance and feel, as opposed to the leaves of Diphasiastrum, which are scale-like and tightly appressed to the branches, giving the plant a smooth texture.
Ref: Haines (2003a); Hickey (1977); Øllgaard In Kramer & Green (1990); Petlewski (2020); Wagner & Beitel (1993) In Flora of North America Editorial Committee (1993b); Wagner, Beitel, & Moran (1989); Zhang & Iwatsuki in FoC (2013). Show full citations.