A modified, step-by-step procedure for the gentle bleaching of delicate fossil leaf cuticles

Cuticular analysis has long been used by palaeobotanists for the identification of fossil leaves, and a variety of chemical procedures has been developed to extract and prepare fossil cuticles. However, even commonly used solutions may be too harsh for the preparation of extremely delicate cuticles. Here we offer a step-by-step protocol for the preparation of fragile conifer cuticles using sodium hypochlorite, otherwise known as household bleach. Conifer needles from the Miocene lignites of the Adendorf and Hambach open-mine pits in western Germany were prepared using a mild solution of this oxidizing agent. The cuticles had proven to be too fragile for most maceration chemicals, including Schulze’s reagent, which even disintegrated the cuticles that were given a protective coating. However, it was discovered that trimming the leaf margins and damaged areas prior to a short exposure to 5–10% sodium hypochlorite solution resulted in the good preparation of the cuticle. Furthermore, this modified method allowed for the preparation of large areas of leaf. While this procedure may not be suitable for all cuticles, it is offered here as an easy and gentle method for preparing extremely delicate conifer cuticles that are destroyed by other chemicals and protocols.