Abstract
Epidermal characters of nine of the Central European Equisetum species were documented using both scanning electron and light microscopy. The arrangement of silica pilulae on the subsidiary cells of stomata as well as the type and the arrangement of papillae on the ridges of main stems and branches allow an unambiguous identification of the species even in the powdered state. A key for the identification is presented, and recommendations for an improved text for the monograph in the European Pharmacopeia are given.
Highlights
The unambiguous identification of individuals of the genus Equisetum sometimes is a challenge even when complete herbarium specimens are on hand
In the monograph of Equisetum arvense of the European Pharmacopoeia emphasis is laid on the paracytic stomata with typical ridges of the superimposed subsidiary cells and on U-shaped epidermal cells, which should be discernible in a
In order to provide feasible characters for the proof of identity, the objective of this study was a systematic collection of characters of the stomata, the epidermal cells and of the structure of the ridges of Central European Equisetum species by means of light microscopy with support of scanning electron microscopy (SEM), leading to a proposal for the monograph in the European Pharmacopoeia
Summary
The unambiguous identification of individuals of the genus Equisetum sometimes is a challenge even when complete herbarium specimens are on hand. Botanical keys [e.g. I]recommend the preparation of transverse sections of the stems: the proportion of the hollows in the stem in combination with morphological characters of the nodes and leaf sheaths should allow a determination of the species. In the monograph of Equisetum arvense of the European Pharmacopoeia emphasis is laid on the paracytic stomata with typical ridges of the superimposed subsidiary cells and on U-shaped epidermal cells, which should be discernible in a. Our preliminary investigations revealed that the mentioned characters of the stomata are present in all species of the genus Equisetum. The U-shaped epidermal cells are characters of the ridges of the branches, which are typically seen in the surface view. A revision of the monograph seemed to be appropriate
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