Stem Morphology and Anatomy in Amaranthus L. (Amaranthaceae), Taxonomic Significance

COSTEA, MIHAI (Department of Botany, University of Agronomical Sciences, Bucharest, Romania) and DARLEEN DEMASON (Botany and Plant Sciences, University of California, Riverside, CA 92521). Stem morphology and anatomy in Amaranthus L. (Amaranthaceae) taxonomic-significance. J. Torrey Bot. Soc. 128: 254-281. 2001.-The range of variation within the genus Amaranthus L. (Amaranthaceae) is described for a number of stem characters including: morphology, epidermis, primary stem vasculature and mechanism of secondary growth. The results provide new characters (phyllotaxy, complexity of leaf vascular supply and relative amount of secondary growth) that support (1) a new infrageneric classification (subgenus Amaranthus vs subgenus Albersia (Kunth)Gren. & Dodr.), and (2) the separation within the "hybridus" complex of cultivated amaranths (A. caudatus L., A. cruentus L. and A. hypochondriacus L.) from their presumed wild ancestors (A. hybridus L. subsp. quitensis (Kunth) Costea & Carretero, A. hybridus L. subsp. hybridus and A. powellii S. Wats. subsp. powellii respectively).