Surface Printing of Plant Leaves for Phylogenetic Studies

Abstract

A solution of plastic consisting of toluene, 720 ml; methanol, 180 ml; ethyl cellulose (Ethocel, standard 7 CPS), 250 gm; and Dow resin 276 V-2, 75 gm is applied to a leaf surface which has been dampened with toluene. The plastic is spread to a thin film with the edge of a card and allowed to dry. After drying, the plastic may be peeled from the leaf surface and either stored dry in a small envelope or mounted permanently on a microscope slide. Permanent mounts are prepared by placing a small section of the peel from the upper and lower surfaces of the leaf on a microscope slide and covering with a No. 1 cover glass. A small spot of balsam on each corner of the cover glass secures the glass in position. This air mount has proved to be superior to water, glycerol or balsam mounts. Fresh leaves are washed with a mild detergent before application of the plastic. Herbarium specimens are soaked in water overnight to restore the leaf to a semiturgid condition. Five species of different plant families have been illustrated to show the diagnostic features of the surface of the cuticle. An isolated layer of epidermal cells obtained by chemical maceration permitted cell and imprint comparison. The re-marKable amount of detail shown by the prints is an aid for phylogenetic studies and may make the recognition of fossil cuticles possible.