Selaginella kraussiana (Kunze) A.Braun

Terrestrial plants. Stems far-creeping, up to 420 mm long, irregularly and widely branched, branches not overlapping except at the stem apices, forming a loose, prostrate mat with apices of ultimate branches upturned; stems yellow-brown proximally, green distally; longest branches 25–130 mm long. Roots arising from axils of branches, occurring throughout the length of the stems. Leaves widely spaced on creeping stems, but imbricate on ultimate branches, pale green proximally, dark green at branch apices, minutely toothed on margins, bases cordate, of two sizes; those in the two lateral rows larger, 2.5–4 mm long, 1.0–2.3 mm wide, spreading, ovate or rarely elliptic, apices acute; those in the two upper rows smaller, 1.5–2.5 mm long, 0.5–1.3 mm wide, closely appressed to stem, ovate, acute to acuminate. Strobili lateral on ultimate branches, sessile, 4–15 mm long, 1.4–2.5 mm diameter, round in cross-section, inconspicuous. Sporophylls similar to leaves of upper rows but smaller and more acuminate, 1.0–1.6 mm long, monomorphic, arranged in four ranks. Megaspores cream to white, with surface ridges forming 5–6-sided polygons. Microspores cream to buff, with long spines projecting from the surface.

Selaginella kraussiana is now a widespread weed in New Zealand and easily the most common of the three introduced species. Its prostrate and irregularly branching habit with roots produced throughout the length of the stem readily distinguish it from S. moellendorffii, which produces erect, aerial, frond-like branching systems with roots at the base. Selaginella kraussiana is similar to S. martensii but the latter has a suberect habit with ultimate branches upturned in the distal half, and roots produced only in the proximal half. Branches are more widely spaced in S. kraussiana and rarely overlapping, whereas in S. martensii they regularly overlap. The leaf margins are minutely toothed in S. kraussiana but finely ciliate in S. martensii. The microspores of S. kraussiana have distinctive surface spines and the megaspores have irregular hexagonal ridges (Large & Braggins 1991, figs 49–57).

Selaginella kraussiana grows on damp banks, tracksides, stream banks, river terraces, forest margins, and in generally shady and damp places under kauri, podocarp, broadleaved, kānuka forest and introduced trees, and in scrub or amongst introduced grasses. It also occurs in parks, gardens, shade houses, cemeteries, picnic areas and lawns. It spreads readily from vegetative fragments.

Cheeseman (1919, p. 92, as Selaginella denticulata). Voucher AK 110931, Pākaraka, Bay of Islands. Cheeseman noted that it had been known for many years as a garden escape at Pākaraka, and had lately appeared in great abundance on the banks of several swampy creeks in the neighbourhood. He also remarked that it was known in several localities near Wellington, and anticipated that it would spread further.

The species was misidentified by Cheeseman (1919, 1925) as Selaginella denticulata Link.