He noted that 24-hour patterns in the movement of the leaves of the plant Mimosa pudica continued even when the plants were kept in constant darkness, in the first experiment to attempt to distinguish an endogenous clock from responses to daily stimuli.
Ia mencatat bahwa pola 24 jam pada gerakan daun tanaman putri malu terus berlanjut bahkan ketika tanaman disimpan dalam kegelapan konstan, pada percobaan pertama untuk mencoba membedakan jam endogen dari tanggapan menuju rangsangan sehari-hari.