MORPHOLOGICAL AND HISTOLOGICAL STUDIES OF CHINESE LICORICE

Licorice consisting of the root and rhizome (i. e. stolons) of several Glycyrrhiza species (Family Leguminosae) has been used since ancient times as a useful drug and is well known in the East and West. The plant origin specified in the Chinese Pharmacopoea 1985 edition includes Glycyrrhiza uralensis Fisch., G. inflata Bat. and G. glabra L.. Among these species, the first is considered the best in quality and most widely used, the other two are also used in many parts of China. Besides, there are also three other species, viz. G. eurycarpa P. Q. Li, G. aspera Pall. and G. yunnanensis Cheng f. et L. K. Tai ex P. C. Li, being used in certain districts of China.In this paper, the morphological and histological characters of crude drugs derived from the above six Glyeyrrhiza species are discribed and compared, and illustrated with line drawings. The morphological and microscopical simillarities and differences found among these species are summarized, and a key for identification of the crude drugs are presented.It is found that the parenchymatous cells surrounding the fibre-bundles are cubical in form and each contains a prism of calcium oxalate in all the six licorice species studied, the number of crystalliferous cells in G. yunnanensis is much less than that in other species. The calcium oxalate crystals also exist in parenchymatous cells of other tissues, such as phelloderm, cortex and pith, but they are more abundant in the pith of the rhizome of G. aspera. The vessel segments usually possess a tail at one end. The tails are much longer in G. inflata, being 60～130 μm in length, about two times the length of vessel body. The characters of phloemand xylem fibres, brownish coloured cell content, medullary ray and pith cells are also useful for identification. The primary xylem of all the six roots is triarch or tetrach, not tetrach only as reported by previous authors.