Studies of attached and detached leaves of Euphorbia caducifolia, the latter collected from morphologically different plants, suggested that this species exhibited typical crassulacean features of acid metabolism. Fluctuations in acidity were found to be due mostly to the appearance and disappearance of malic acid in dark and light respectively. Deacidification also took place when leaves were kept in dark for a longer period. The TAN showed a fall when the leaves aged and were about to fall. A remarkable feature found in this species was the high percentage of total acids which ranged up to 8240 mg/100 g fresh weight of leaves, together with great differences in the constituents analysed. This suggests that morphological diversity is correlated with physiological diversity.