“…The same conclusion was drawn by SHREVE (1914) from similar experiments. TRELEASE and LIVINGSTON (1916), using the porometer method, found that in the course of the day the maximum of stomatal aperture was reached some hours after the maximum of transpiration, so that another mechanism seemed to play a role in regulating transpiration. KNIGHT (1917,1922) also accepted a dual influence on the transpiration rate: -the incipient drying of the cell walls would control it in case of bright weather and wide open stomata, while at low light intensities and small apertures the stomata themselves would be the main controlling factor.…”