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The occurrence of crassulacean acid metabolism (CAM) among epiphytes and related plant species from tropical and subtropical rainforests in Eastern Australia was investigated. As judged from δ¹³C value and the absence of Kranz anatomy, indications of CAM were found in 66 species belonging to the families, Polypodiaceae (3), Orchidaceae (55), Asclepiadaceae (6) and Rubiaceae (2).

Two thirds of orchidaceous plants examined appeared to use CAM. Those species with thicker leaves generally had less negative δ¹³C values, as did those species growing on more exposed sites; leaves thicker than about 1 mm in most species yielded δ¹³C values indicative of pronounced CAM. Two leafless species, Chiloschista phyllorhiza and Taeniophyllum malianum, which depend on chloroplast-containing, stomata-less roots for photosynthesis also showed δ¹³C values typical of CAM. Pseudobulbs …