About Wijkia extenuata (Brid.) H.A.Crum
Wijkia extenuata (Brid.) H.A.Crum is a variable small to medium-sized moss species, with both of its recognized varieties sharing most core characteristics. Both varieties grow as stiff, compactly branched plants that can form loose tufts, or grow as soft, pendulous forms. Their color ranges from yellow to brown-green or dark green, which turns golden as they age, and they form loosely interwoven mats. Stems are red, irregularly creeping, reach around 12 cm (4.7 in) long, and branch bipinnately or subpinnately. Branches grow pinnately or as simple branches, and are either ascendant or creeping; branchlets near branch tips often produce multiple flagelliform, microphyllous structures. The most consistent distinguishing feature between the two varieties relates to dominant branch type. The variety caudata is defined by its "branch-only" growth habit, which does not develop flagelliform branches. Stem and branch leaves are differentiated, and lack a costa. Stem leaves are broadly ovate to lanceolate, appressed to erect and wide-spreading when dry, and abruptly narrow to a slender, occasionally serrulate, piliferous apex. Primary stem leaves are roughly 1โ2 mm long, while secondary stem leaves average around 1.5 mm (0.059 in) long. Branch leaves are lanceolate to ovate-lanceolate, smaller at 0.5โ1 mm (0.020โ0.039 in) long, sharply toothed, more slender than stem leaves, and grow erect to erect-spreading. They are concave and taper gradually to a short acuminate apex, lack a piliferous point, and sometimes have strongly serrulate margins that extend all the way to the base. This species is visually similar to Calliergonella cuspidata, but can be distinguished by its distinctive long leaf hairpoint. Wijkia extenuata reproduces asexually via specialized flagelliform, deciduous branchlets that have foliose, deltoid pseudoparaphyllia. Its perichaetia are conspicuous, scattered, and grow from stems; inner perichaetial leaves are erect with a long, sharply toothed acumen. Setae are red-brown, smooth, elongated, twisted to the left in their upper portion, and measure 15โ40 mm (0.59โ1.57 in) long. Calyptrae are smooth and cucullate. Capsules are roughly 1.5 mm (0.059 in) long, asymmetric, horizontal, oblong-cylindric below the mouth, and have a short neck. The annulus is differentiated; the operculum has a high-conic, blunt, arched base, and lacks a long rostrum. Peristomes are pale and double. They feature 16 strongly bordered, shouldered exostome teeth with a zig-zag median line and trabeculae on the inner surface; the endostome has 16 perforated or keeled segments, a high basal membrane, and cilia arranged singly or in pairs. Spores are spherical, papillose, and around 12โ16 ฮผm in diameter. Both varieties of Wijkia extenuata most commonly grow on logs, decaying wood, and tree bases, as epiphytes, and rarely grow on rocks or soil. It is a common species in wet forests and rainforests, distributed across eastern Australia (Queensland, New South Wales, Australian Capital Territory, Victoria, and Tasmania), Papua New Guinea, New Zealand, and Pacific island nations including Fiji.
