Compare the microscopic characteristics of stems of the 24 Dendrobium species utilized in the traditional Chinese medicine "Shihu".

Shihu is a famous Chinese Materia Medica derived from species of the Dendrobium. In order to differentiate 24 Dendrobium species, microscopic features of the 24 Dendrobium species were systemically observed, including the trend of vascular bundle number with different internodes and the transverse section characteristics of stem. The results indicate that the thickness of cuticle, the level of thickening of epidermal cells and cell types, the number of vascular bundles, the shape of vascular bundle sheath, the type and distribution of calcium oxalate crystals, the presence or absence of silica masses can be used to authenticate the 24 Dendrobium species. In addition, the number of vascular bundles in stems of 24 Dendrobium species also have changed at different internodes, and showed a trend of first increasing and then decreasing. For some specific species, the vascular bundle numbers had typical differences, which can provide some support for the identification of Dendrobium plants. Thus, using the multiple microscopic characteristics of stems can identify the Dendrobium plants effectively and quickly.