A space lit entirely with green light corresponds to the absorption spectrum of chlorophyll A. Here, the roles are reversed: it is no longer a space designed for the visitor but for the preservation of plants and their representation. Green light is used at the entrance to the herbarium conservation rooms of the Museum of Natural History in Paris to attract insects and avoid contamination. Here, it has another use. It helps to preserve chlorophyll pigment ink: observation of the herbarium and the botanical plates under the green light at 550 nm forces the eye to distinguish tone-on-tone drawings, and hence the visitor to adapt to a universe designed to preserve a memorial trace of plants.