Lycopodium clavatum L. 1753

Lycopodium clavatum L. (1753: 1101). Fig. 21 A–B

Lepidotis clavata (L.) Palisot (1805: 108).—Type: Herb. Burser XX: 49 (UPS). Lectotype designated by Jonsell & Jarvis (1994: 147).

Plants creeping, trailing, or hanging over banks. Main stem usually above ground, rooting with long intervals, 2–3 (–4) mm thick excl. leaves. Aerial shoots ascending to stiffly erect, to at least 50 cm tall, repeatedly unequally branched, with strongly diverging to almost parallel branchlets. Ultimate branchlets terete. Leaves borne in low alternating spirals or whorls of 6–8 (–10), forming 12–16 (–20) indistinct longitudinal ranks, patent to ascending or imbricate, linearacicular, 6–8 (–10) × 0.5–0.8 mm, terminating in a long colorless hair or membranous apex, with smooth to sparsely denticulate margins. Strobili sessile or pedunculate. Peduncles, when present, terminating main branchlets, erect, to 30 cm long, simple, or branched and bearing to 6 pedicellate strobili. Peduncle leaves distant, appressed, reduced in length, partially membranous. Strobili 1.5–6 (–8) cm long, ca 6 mm in diam. including sporophylls, sometimes forked. Sporophylls borne in alternating whorls of 5–6, forming 10–12 longitudinal ranks, subpeltate, with a median, basiscopic, membranous wing on the stalk, connecting the basiscopic flap of the exterior face to the strobilus axis, with triangular-ovate to rhombic-ovate, acuminate exterior face, with usually broadly scarious, dentate to erose-laciniate margins. Sporangia 1.3–1.6 mm wide. Spores reticulate on all faces.

­­­ Distribution:—Almost cosmopolitan, in humid temperate and boreal regions of the northern hemisphere, and on tropical mountains of the Old and New World. Not known from Australia.

Notes:—The species is highly variable and adaptive to external factors. Lycopodium clavatum exhibits an almost continuous series of forms, from amply branched plants with diverging branches and spreading, soft leaves, and long branched peduncles, growing in moist, warm, sheltered habitats,-to small, compact, parallel-branched plants with more imbricate and firm leaves, and lacking, or short, simple or once forked peduncles, belonging to cold, exposed habitats e. g. at high elevations. The latter forms are here recognized as the subspecies contiguum. Corresponding monostachyous forms are found in the Arctic. The two subspecies recognized here are often considered to be distinct species. However, there are many intermediate forms which we are unable to place in one or the other taxon with certainty. These intermediates form normal spores and have normal meioses. Because in most cases the two forms are recognizable and are generally ecologically differentiated, two subspecies are treated here.