Grewia nagensium Prain vs Grewia denticulata Wall. ex Prain (Tiliaceae), which is to be accepted?

Abstract

Prain (1900: 168) described the species Grewia nagensium based on specimens collected from Assam and Nagaland in Northeast India. Few months later, while preparing “A second century of new and rare Indian plants”, Prain (1901: 10) noted that his G. nagensium is indeed G. denticulata Wall. ex Voigt (1845: 128) and treated the former as a synonym of latter. However, “G. denticulata Wall. ex Voigt” is a nomen nudum as Voigt did not provide any description. Kanjilal et al. (1934) in their account of Flora of Assam mentioned only “Grewia denticulata, Wall. Ann. Roy. Bot. Gard. Calc. lx. 10. t. 12” and did not discuss its nomenclature. After about 6 decades, in Flora of India, Daniel & Chandrabose (1993) accepted the name as “Grewia denticulata Wall. ex Prain” (1901), and cited Grewia nagensium Prain (1900) as its synonym, which was followed by the Chowdhery et al. (1996). In some taxonomic database such as The Plant List (2013 onwards) and Tropicos (2015) the name Grewia denticulata Wall. ex Prain is also accepted! The name G. denticulata was indeed validly published by Prain (1901), with a full description and plate with analyses, but as Prain ascribed it to “Wall. ex Voigt” (i.e. essentially, to Voigt) it is to be cited as G. denticulata Voigt ex Prain. However, it is an illegitimate, nomenclaturally superfluous name, as the earlier name G. nagensium Prain was cited in synonymy. G. denticulata Voigt ex Prain is therefore unavailable for use and is to be treated as a synonym.