The New Zealand moss Canalohypopterygium tamariscinum (Hypopterygiaceae) is characterised by rudimentary branches. These branches have cavities that are filled with oil, which is a feature in mosses which is shared only with Catharomnion ciliatum (Hypopterygiaceae). The oil of Canalohypopteiygium tamariscinum mainly consists of apolar hydrocarbons. This oil may have an energy storage function, serve to repel (in)vertebrates, fungi, or bacteria, or may be an adaptation to life in humid or harsh environmental conditions. Alternatively, the oil might have had a distinct function in the past, which has been lost in the course of evolution.