Mimosa pudica, a sensitive leguminous plant, lends itself to studies of different types of stimuli and of their inhibitors. Observations are reported concerning their responses to electrical and mechanical stimuli, inhibition by steroid cardenolides, the role of the phytochrome system under daylight conditions and of the transport ATP-ase in the primary pulvini. Free running leaf movements appear to follow the red/far red light ratios from sunrise to sunset during the months of observation. Mechanical stimulation evoked maximum response during periods of minimum R/FR, while electrical shocks were most effective during periods of maximum R/FR. Digitoxin, digoxin and ouabain inhibited leaf movements in response to these stimuli during periods of reduced R/FR, when the supply of ATP was apparently minimal. The interrelationships between R/FR, PF, PFR and transport ATP-ase are discussed. The degree of illuminance of the plants tends to affect free running leaf movements with statistical significance positively or negatively depending on its intensity. Methods for calculating R/FR under local greenhouse conditions have been applied by using observations from other localities and from above the atmosphere measurements.