The identities of two historical names, Zingiber neesanum (≡ Alpinia neesana) and Z. macrostachyum are re-investigated. Both have been considered to represent the same taxonomic entity by various workers in the past 160 years. Yet, based on traditional usage, they were applied to two distinct taxa occurring in the Western Ghats (India), both superficially similar by having long-stalked inflorescences, but much distinct in flower colour and overall morphology. Alpinia neesana was originally described only from fruiting material, while Z. macrostachyum was described from flowering material of a species with white flowers. Dalzell's presumption that his taxon was identical to Graham's, and unambiguous inclusion of A. neesana in his description made his name nomenclaturally superfluous and illegitimate. After realising the illegitimacy of Dalzell's name, a new combination was created in Zingiber for A. neesana. The name Z. neesanum continued to be applied sensu Dalzell to the white-flowered species mainly in the central and southern Western Ghats, but it was also applied to a yellow-flowered species in the northern Western Ghats, for which another name, Z. diwakarianum, was proposed recently. Despite the absence of any original material relating to Graham's or Dalzell's descriptions, re-collections from the type localities prove beyond any reasonable doubt that the yellow-flowered species is the true Z. neesanum, making Z. diwakarianum a synonym, and that the existing name Z. anamalayanum has to be applied to the white-flowered species, originally described by Dalzell as Z. macrostachyum. The significance of authentic primary data sources concerning botanical history such as correspondence and manuscripts of collectors and botanists, and the importance of making these resources widely accessible through digitisation are highlighted.

Graham's posthumous publication (Cat. Pl. Bombay, 1839) was completed by Joseph Nimmo, in addition to contributing several new species in it. Croton gibsonianus Nimmo and C. lawianus Nimmo (Euphorbiaceae) were part of this addition, and both were described based on Gibson's collection from adjoining localities in the Western India. As the diagnosis of the latter species was scant, it was subsequently interpreted in different genera viz. Dimorphocalyx, Trigonostemon and Tritaxis. Due to misinterpretation of the protologue and Gibson's Croton collection housed at K, the name C. lawianus was wrongly applied to C. gibsonianus by subsequent authors. This inadvertent application of name is corrected here and referred to the hitherto undescribed new species C. chakrabartyi. Our recent collection of C. gibsonianus has turned out to be a rediscovery after 170 years. The nomenclature, description, photographs, and distribution of C. gibsonianus are provided to avoid further taxonomic ambiguity.