Siphula decumbens Nyl.
S. medioxima Nyl., Lich. N.Z.: 15 (1888).
S. mooreae Zahlbr., Denkschr. Akad. Wiss. Wien math.-naturwiss. Kl. 104: 365 (1941).
Lectotype: New Zealand. Greymouth, supra terram. R. Helms 127, 1886, H-NYL!
S. medioxima. Type: New Zealand. ? R. Helms, H-NYL.
S. mooreae. Type: New Zealand. South Auckland, Mt Moehau, Coromandel Peninsula, c. 850 m, on soil. L.B. Moore ZA299, CHR381012.
Thallus lobes variable, narrow, 2-6 mm wide, 0.3-3(-4) cm tall, ± terete or flattened, rarely simple, strap-like, margins entire or variously notched and incised, apices rounded, furcate or irregularly pectinate, ± unilaterally thickened, crowded, congested. Surface ± smooth, coriaceous to roughened, scabrid-areolate or furrowed, in humid, low-light sites often ± fenestrate with ragged, lacerate margins, chalky white in subalpine exposed sites, becoming greenish in sheltered, humid or shaded sites, 0.3 mm thick, smoother and more coriaceous in exposed subalpine habitats, 0.05-0.1 mm thick in shade forms. Chemistry: Medulla K+ yellow or -, Pd+ yellow. Two chemodemes appear to be present, a thamnolic acid chemodeme (K+) and a chemodeme with baeomycesic acid (K-).
N: North Auckland (Herekino Gorge, Great Barrier I.). Auckland (Hunua Ra., Coromandel Ra., Te Aroha, Kaimai Ra.). Wellington (Tararua Ra.). S: Nelson (Pakawau) to Southland (Fiordland and Awarua bog). St: Widely distributed, coastal and inland, s.l. to 2000 m.
Cosmopolitan
S. decumbens is the most widespread species of Siphula in New Zealand and also the most variable. It occupies a variety of habitats from subalpine soils at sea level around Foveaux Strait and on Stewart I., to alpine soils in most mountainous areas of South I., to epiphytic moss communities on tree trunks and stumps in sites in north Westland, Nelson, the Coromandel Range, Great Barrier I., and North Auckland. When growing among bryophytes in shaded, ± humid habitats, thalli of S. decumbens are thinner, flatter, more delicate, marginally lacerate-fenestrate with a granularareolate surface with a pronounced greenish or blue-green colour. Forms from exposed alpine soils are shorter, thicker, more coriaceous and crowded-congested, and may yet prove to be specifically distinct. In some alpine areas along tracks well used by trampers and climbers, thalli of S. decumbens are fragmented and dispersed in the soil at the side of the tracks. In such situations it is possible to observe a change in the morphology of S. decumbens from the alpine grassland type, to the lacerate-fenestrate type characteristic of forest conditions, as fragments are carried down through subalpine scrub into the upper reaches of the forest and establish there in damper and more shaded conditions. It is possible, too, that in certain areas, trampling by deer also influences the distribution of this species.
