Darwin’s Experiment

Darwin’s method for observing plant movements involved placing a plant behind a glass plate, then marking and measuring the plant’s position on the glass throughout the day against a stationary reference point placed behind the plant. By varying the distance between the plant, the reference point and the glass plate, Darwin was able to control the magnification of the plant movements, allowing him to detect movements over periods of just several minutes.

By connecting the dots, Darwin was able to create graphs that illustrated how much the plant had moved over a period of time. As his notes and data reveal, Darwin observed that a plant’s movement was in response to a number of stimuli. The plant seemed to almost consciously reposition itself closer to resources or away from harm.

the leaflets…of some plants are known to be injured by too much light; and when the sun shines brightly on them, they move…so that they direct their edges towards the light, and thus they escape being injured.

– Charles Darwin
The Power of Movement in Plants, 1880