Notes on Huperzia

According to the current view, the genus Huperzia Bernh. (Lycopodiaceae) comprises two taxa in Finland (and Europe): H. selago and H. appressa. Some people recognize the latter as a subspecies or a variety. My long-time observations, mainly in southern and central Finland, suggest that actually more than two taxa may exist. In fact, at least five taxa appear to be discernible. Moreover, some plants do not fit readily even with any of these five morphs. In addition, the limit between H. selago and H. appressa, in particular, requires special attention; intermediates (true hybrids?) possibly occur.
    The annual constrictions are lacking or indistinct in all the Finnish taxa. Stomates are present on both sides of the leaves in all of them. I have not yet examined the spores of our Huperzia plants.

Fig. 1. Huperzia selago (L.) Bernh. ex Schrank & Mart. s. str. (Finland, Tampere, Viitapohja, 1990). –  Image: Harri Harmaja (scanned from dried specimen). – Shoot growth probably determinate. Grass-green, paler green in places; at times with browned areas. Fertile part longer than the sterile one in an annual growth, i.e. sporangia develop almost throughout the mature portion of a shoot. Gemmiferous branchlets present, rather persistent, occurring in one whorl at upper end of sterile zone of annual growth. Gemmae broad. Leaves in distinct longitudinal rows, their direction variable within a shoot (ascending, patent or somewhat appressed), thick, with rugulose (below) to fairly regularly denticulate (shoot upwards) margins in their upper halves; throughout the shoot 5-6 × 1.3-1.7 mm, rather broadly lanceolate or almost triangular, with margins hardly parallel. The sporangia are probably the largest among the Finnish taxa.
    This taxon is distributed in whole Finland but is not common. In the north it probably does not favour specific habitats but in the south it seems to prefer the N and NE slopes of oligotrophic rocky hills. The depicted plant grew accompanied by the northern lichen Opisteria arctica.

Fig. 2. Huperzia appressa (Bach.Pyl. ex Desv.) Á.Löve & D.Löve (Finland, Äänekoski, Hietama, 1988). – Image: Harri Harmaja (scanned from dried specimen). – Shoot growth probably determinate. Yellow-green.  Fertile part longer than the sterile one in an annual growth, i.e. sporangia develop almost throughout the mature portion of a shoot. Gemmiferous branchlets present, persistent, occurring in one whorl at upper end of sterile zone of annual growth. Gemmae rather narrow. Leaves in distinct longitudinal rows, appressed to ascending (probably less appressed in more shady habitats and more so in full light), with slightly rugulose margins at their upper halves (some leaves appearing entire); in basal portion of shoot 3.5-5.0 × 1-1.2 mm, lanceolate, with parallel margins in their lower halves; in fertile portion sterile leaves scanty being like basal leaves but smaller, sporophylls 3.0-4.5 × 1.1-1.4 mm, ovate or narrowly triangular.
    This taxon is common in northernmost Finland (Lapland) where it dwells many kinds of more or less open habitats, both dry and moist ones. It becomes infrequent towards the south. I have found H. appressa a few times in southern and central Finland, in mesotrophic and eutrophic mires; it is also reported to occur in rock outcrops in these parts of the country. The depicted plant was found in a meso-eutrophic fen with e. g. Dactylorhiza incarnata ssp. incarnata, Drosera intermedia and Juncus stygius near-by.
    H. arctica (Grossh. ex Tolm.) Sipliv. may be a synonym..

Fig. 3. Huperzia taxon 1 (Finland, Lohja, Koski, 1994). – Image: Harri Harmaja (scanned from dried specimen). – Shoot growth probably determinate. Pale grass-green with faint yellowish tinge; conspicuously very pale straw-coloured towards base. Fertile part clearly longer than the sterile one in an annual growth, i.e. sporangia develop almost throughout the mature portion of a shoot. Gemmiferous branchlets present, persistent, occurring (i) in one whorl at upper end of sterile zone of annual growth and (ii) scattered in the fertile zone; annual growths being short, the branchlets thus appear to be irregularly distributed through the whole mature portion of shoot. Gemmae moderately wide. Leaves in distinct longitudinal rows (probably 8), patent or ascending at base, ascending upwards, with long-tapered and upwards curved apices, and entire margins; in basal portion of shoot 6-7 × 1 mm, acicular, with parallel sides most of their length; in fertile portion 3.5-4.5 × 1.0-1.2 mm, lanceolate to ovate.
    Once found by me in the N slope of the top of a high oligotrophic rocky hill, among mosses and lichens (e.g., Cladonia amaurocrea), near patches of Sphagnum. A pronouncedly humid atmosphere prevailed in the habitat; the lichens Alectoria sarmentosa and Trapeliopsis pseudogranulosa, known as indicators of humid microclimate, grew near by.
    The present plant bears some resemblance to H. chinensis (Christ) Ching (incl. H. miyoshiana (Makino) Ching) of Asia and North America, but has taller leaves.

Fig. 4. Huperzia taxon 2 (Finland, Lohja, Immula, 1988). – Image: Harri Harmaja (scanned from dried specimen). – Shoot growth indeterminate: the youngest and most active portion is erect; downwards the older shoot gradually loses its photosynthesizing capacity and becomes more or less horizontal along the ground, partly within litter and mosses. The erect portion of the shoot is dark green, downwards the shoot is yellowish-green, still older portion being pale brown (possibly with some fulvous tinge; this brown portion finally dies and gets broken when the plant base is dug up). Fertile zone and sterile zone in an annual growth sometimes equally long but more often the fertile one longer (hence distinct sporiferous and sterile zones alternate in the mature portion of a shoot). Gemmiferous branchlets usually absent (when present, occurring at upper end of sterile zone of annual growth; gemmae probably moderately wide). Leaves in distinct longitudinal rows (8, 9, 10?), completely spreading (patent) or partly somewhat ascending, with verruculose or fairly distinctly denticulate margins in their upper halves; throughout the shoot 4.5-7.5 × 1.1-1.3 mm, lanceolate-linear with partly parallel sides, the sporophylls being often relatively slightly broader (lanceolate-narrowly triangular) than sterile leaves. Sporangia 1.4-1.6 mm broad, on the average slightly broader than the sporophyll base.
    Occurs on forest ground (including moist places), at basal terraces of rock outcrops, on talus slopes and boulders below rock walls, certain kinds of peatland, shores of brooks and lakes, rarely on rock surfaces facing north (hardly in fully open habitats); common except in the north. The habitats are more shady and less oligotrophic than those of the three preceding taxa; the present plant is the only hygrophilic one of our taxa, not rarely occurring with e. g. Lycopodium annotinum s. str. This taxon may be regarded as an ecological – somewhat also morphological – vicariate of H. lucidula (Michaux) Trevisan of eastern North America.
    The nomenclature of the present taxon is extremely intricate. It apparently lacks a legitimate name at the species level. Sometimes, it has been called as H. selago var. patens (P.Beauv.) Trevisan. Anyway, the name Lycopodium selago L. forma patentissima J.Schmidt, partly based on Finnish material, refers to the present plant.

Fig. 5. Huperzia taxon 3 (Finland, Tampere, Viitapohja, 1992). – Image: Harri Harmaja (scanned from dried specimen). – Only juvenile, sterile plants of this kind were found. This morph is peculiar as having oblanceolate leaves, i.e. the latter are broadest above their middle. The leaves attain a size of 6 × 1.5 mm, and the margins of their upper halves have small, sharp teeth. The adaxial stomates of the leaves are scanty. Once found by me in a low, half-shady, eutrophic rock outcrop. The leaves of this plant somewhat resemble those of H. lucidula (Michaux) Trevisan of eastern North America.
    According to a few observations of mine on herbarium material and literature, the leaves of a juvenile Huperzia plant (e.g., of one germinating from a gemma) may be clearly different (such as oblanceolate) from the later ones. However, this unusual leaf shape may be diagnostic in this case, especially as also the distribution of the stomates is peculiar.

Warren H. Wagner Jr. & Joseph M. Beitel treat the genus comprehensively in the online pages of Flora of North America. It is noteworthy that they consider interspecific hybridization to be a common phenomenon in the genus. Elsewhere, however, the opinions continue to be controversial, and the taxonomy of the genus in Europe is urgently in the need of a revision: see e.g. the treatments of Huperzia in the Flora of the Canadian Arctic Archipelago and the Panarctic Flora Project.