Henri Edgard Devaux (6 July 1862 – 14 March 1956) was a French botanist, biophysicist, and plant physiologist who worked on gas exchange and membranes.

He then went to the University of Sorbonne and received a doctorate in 1889 for work under Gaston Bonnier on gas exchange in plant tissues.

He also made use of mercury and with this approach, using a known amount of liquid, he was able to compute the surface area of circular mono-layers of various fats, oils and proteins and estimate molecular weights.

[1][2][3][4] Devaux was brought up in a religious Protestant upbringing in a family that included many generations who worked as sailors and farmers.

From 1890 he became more religious and often wrote on his spiritual views in his laboratory notes and even some of his scientific works.