Flora of New Zealand Series

Thallus lobate, white, creamish, pinkish or greenish, laterally compressed to ± terete, often crowded, thick or thin, often fragile, on soil or amongst moss, anchored with a ± well-developed rooting system. Roots terete, dendroid, 0.5-1.5 cm long, simple to complexly branching. Lobes laterally compressed, margins entire or lacerate, often sinuous and with or without slight lateral thickening at apices. Medulla white. Photobiont green, Trebouxia. Apothecia unknown.

Siphula is a cosmopolitan genus of c. 30 species of which 7 occur in New Zealand. Species are without exception sterile, and are most frequently found in alpine or subalpine habitats, rarely some species are epiphytic amongst mosses on tree trunks in humid, semi-shaded habitats. The genus is best developed in the Southern Hemisphere, and New Zealand appears to be one of the three centres of speciation, the others being southern Africa and South America. A definitive monograph is not yet available but the review of South African species [Mathey Nova Hedwigia 22: 795-878 (1974)] contains useful information. Chemical constituents in Siphula are reviewed by Bendz et al., [ Acta chem. Scand. 19: 1250-1252 (1965)] and J. Santesson [ Acta chem. Scand. 21: 1833-1837 (1967)]. Simple thallus chemistry is useful in separating some species in a genus where few distinguishing characters are present.