Flora of New Zealand Series

Thallus dimorphic. Primary thallus persistent or disappearing, crustose or squamulose to foliose, hyphae rather loose, rarely dense or conglutinate. Upper cortex dense, of ± vertical hyphae. Medulla white, of thick-walled, often conglutinate hyphae. Lower surface usually decorticate. Photobiont green, Trebouxia, conglomerate in an irregular layer in the upper part of the medulla. Podetia, (vertical developments of the stalks of apothecia) grow from upper surface of margins of primary thallus, blunt, pointed or cup-forming (scyphiferous), simple or branched, solid at first, soon becoming hollow, with an outer cortex which may persist or disintegrate, becoming sorediate, verrucose or areolate. Soredia farinose (10-40 µm diam.), granular (40-120-300 µm diam.) often densely encrusted with lichen compounds; corticate granules (100-300 µm diam.) similar to soredia but with a well-developed ± continuous, thin corticate layer. Medulla dense or loose, containing symbiotic algae in outer part: in many species outer medulla becomes arachnoid and the inner medulla becomes hard and horny (chondroid) entirely, or in strands. Base persistent or dying away with growth continuing at apices, apices sterile or with apothecia. Apothecia at tips of podetia (normally larger than diameter of supporting stalk), on margins of cups (scyphi) or on primary squamules, lecideine, red, pale or dark brown or brown-black, margins narrow, or immarginate and convex, solitary or clustered-peltate to compound, confluent, exciple radiate, hypothecium pale to reddish, hymenium 30-70 µm tall, paraphyses slender, 2-5 µm thick, simple or sparingly branched. Asci cylindrical to clavate, 8-spored. Ascospores irregularly biseriate, fusiform, oblong or ovoid, 6-24 × 2-4.5 µm, simple, colourless. Pycnidia at apices of podetia, margins of cups, margins or upper surface of primary squamules, sessile or short-stalked, variable in shape, cylindrical, ovoid, turbinate or capitate, ostiole small or dilated, brown-black, ashy or red, containing a colourless or red jelly. Conidia cylindrical, filiform, straight or curved, 5-14 × 0.5-1 µm.

Cladonia is a widespread and frequently collected genus in New Zealand, distinguished from other lichens by a vertical (secondary) thallus, the podetium*: an elongated, hollow, cylindrical or cup-shaped structure which develops from generative tissue in the horizontal (primary) thallus [Jahns and Beltman Lichenologist 5: 349-367 (1973)]. It is a cosmopolitan genus of c. 300 described species growing on a variety of substrates from sea level to alpine fellfield at 2000 m. Most species in New Zealand are highly xerophytic and grow on barren or acid soils (C. pocillum grows on limestone soils) in heaths or on peat, rotting logs or decaying tussock bases. Some are frequent on roadside banks and cuttings or on a thin veneer of soil overlying rock. Though they occur commonly in areas of both high and low rainfall, in general species avoid permanently saturated substrates. They can withstand both drought and frost. Most species are light demanding and none grow in deep shade. In polluted environments species of Cladonia are rare, with often only basal squamules developed. Some species are mainly montane or subalpine while others appear to be confined to lowland sites. The greatest concentrations of species or of individuals in New Zealand occur on Leptospermum or Dracophyllum heaths, on decaying logs at forest margins, or on dead bases of tussocks margining areas of peat.

Useful information is found in Thomson ["The lichen genus Cladonia in North America". 172 pp. Toronto (1968)]; Martin [ T.R.S.N.Z. (Bot.) 85: 603-632 (1958)] and Ahti [ Annls bot. fenn. 10: 163-184 (1973); Annls bot. fenn. 15: 7-14 (1978); Lichenologist 12 (1): 125-133 (1980); Annls. bot. fenn. 17: 195-243 (1980)]. Chemistry is a useful aid in discriminating species of Cladonia, [Thomson 1968 loc. cit. ; Martin, Tuatara 19: 6-11 (1971); Nourish and Oliver in "Lichenology: Progress and Problems", D.H. Brown, D.L. Hawksworth and R.H. Bailey (Eds): pp. 185-214 (1976); and Huovinen and Ahti, Annls bot. fenn. 19: 225-234 (1982)].

Species of Cladonia show considerable variation in both morphology and chemistry. In the present work 41 species are discussed but it must be stressed that this number gives an incomplete picture of the Cladonia flora. Further collection and examination of populations in the field, especially in alpine, and North I., habitats is necessary before a comprehensive account of the species in New Zealand can be made. William Martin's extensive collections (CHR) are an excellent basis for study and are rapidly being augmented by the North I., Westland and Nelson collections of J.K. Bartlett.

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*Ahti [ Lichenologist 14: 105-113 (1982)] proposes the following definition of podetium (p. 109) "... a podetium is a lichenized, stem-like portion (stipe or discopodium) bearing the hymenial discs and sometimes conidiomata in a fruticose apothecium ...".