Taxonomic Significance of Floral morphology in Identification of South Indian Alternanthera Forsskal (Amaranthaceae)

The genus Alternanthera popularly called 'Joy weed' was established by Forsskal in 1775, coming under the family Amaranthaceae. Amaranthaceae, popularly called 'amaranth family, is a moderately large family with 77 genera and over 840 species (Müller & Borsch, 2005). It is a pantropical family with some genera or species reaching the warmer temperate regions. Nearly one third of the genera of the family are monotypic. The genus can be distinguished from other genera of Amaranthaceae by its two-chambered anthers, pseudostaminodia alternating with fertile (and sometimes sterile) filaments; stigma capitate; inflorescence of solitary or multiple, axillary or terminal globose heads usually without subtending leafy bracts. The genus was treated with confusion in several regional floras which are devoid of updated nomenclature and citation of type specimens. A key to the taxa are provided along with illustration of Androecium and Gynoecium of 6 species to facilitate identification of the taxa.