TABLE 1. Morphological comparisons of Nymphanthus namkadingensis with N. chantaranothaii, N. glaucescens, and N. rubescens. The characteristics are derived from Beille (1927) and Pham (2003) (N. glaucescens & N. rubescens), Chantaranothai (2007), and Li & Gilbert (2008) (N. glaucescens), and Pornpongrungrueng et al. (2019) (N. chantaranothaii). Size of stipules of N. rubescens is measured on digitized herbarium specimens listed in Appendix 1.

Characters	N. namkadingensis	N. chantaranothaii	N. glaucescens	N. rubescens
Size of stipule (mm)	3–9 × 1–2	1.4–2 × 0.1–0.4	1.3–4 × 1.5–2	0.5–1 × 0.5–0.7
Number of lateral nerves of lamina	8–12 pairs	4–7 pairs	4–6 pairs	NA (barely visible)
Length of pedicel (mm)	♂: 4–8, ♀: 10–16	♂: 5–11, ♀: 8–11	♂: 5–15, ♀: 14–25	♂: 1.5, ♀: 2.5
Sepal of staminate and pistillate flowers	apex not fimbriate, margin undulate, almost entire	apex and margin fimbriate	apex and margin fimbriate	apex not fimbriate, margin entire
Disc of pistillate flower	connate, annular	free, obovate	connate, annular	free, rectangular