The genus Justicia was first described by Linnaeus (1753) consisting of 11 species: J. adhatoda, J. betonica, J. chinenfis, J. echioides, J. ecbolium, J. hyffopifolia, J. procumbens, J. purpurea, J. repens, . sexangularis and J. uafuta. The genus was named in honour of James Justice (1698-1783), a Scottish horticulturist and botanist. Justicia has been one of the most controversial genera of Acanthaceae with regard to its taxonomy and nomenclature since Linnaeus’ time. After published work on Justicia by Linnaeus, Britton (1918) chosen J. adhatoda as the type, but it seemed to be the historical type of the generic name when many authors such as Nees (1847), Bentham (1876). Manning & Norris (1985) transferred J. adhatoda to the genus Adhatoda. Hence, J. hyssopifolia was designated under the Article 8 of the International Code of Botanical Nomenclature (ICBN) in the Vienna Code (McNeill et al., 2006) as a new type of the genus by Hitchcock & Green (1929) based on a specimen in the Linnaean herbarium (LINN 28.10). Jarvis (1992) proposed this species as the conserved type of the genus Justicia and its acceptance would evidently maintain usage of the generic name.
The major classifications of Justicia have been variously circumscribed at the infrageneric level (Table 1.3), as follows:
Nees (1847) described the genus Justicia in monograph of the Acanthaceae in De Candolle's Prodromus. He distinguished Justicia in subfamily Echmatacantheae and subtribe Eranthemeae, which is characterised by having seed supported by retinacula. This subtribe comprises of eight genera i.e. Anisacanthus, Anthacanthus, Chamaeranthemum, Chartacanthus, Eranthemum, Justicia, Rhinacanthus and Sericospora. The genus Justicia is characterised by having a deeply 5-lobed calyx, bilabiate corolla, 2 stamens with bithecous anthers. He also split this genus into smaller genera such as Adhatoda Miller, Beloperone Nees, Gendarussa Nees, Rhaphidospora Nees and Rostellularia Nees.
Anderson (1867) divided the genus into five sections; Betonica, Gendarussa, Leptostachya, Rhaphidospora and Rostellaria. Justicia adhatoda was placed into section Betonica, mainly characterised by having a spike inflorescence and bract imbricate. Most species of section Leptostachya are characterised by their anthers lack tails, whereas other sections are described as tailed anthers.
Bentham (1876) classified Justicia by being 4–5-lobed calyx, bilabiate corolla, 2 stamens. He also divided Justicia into 11 sections: Adhatodoides, Amphiscopia, Anisostachya, Betonica, Gendarussa, Harnieria, Hemichoriste, Monechma, Rhaphidospora, Rostellaria and Sarotheca.
Lindau (1895) placed Justicia within the subfamily Acanthoideae, tribe Justicieae. He divided the genus into three subgenera: Dianthera, Eujusticia and Gendarussa, on the basis of pollen morphology. The subgenus Eujusticia is further subdivided into seven sections i.e. Adhatoda, Amphiscopia, Leptostachya, Monechma, Rostellaria, Tyloglossa and Vasica.
Bremekamp (1965) classified the genus as belonging to subfamily Ruellioideae, tribe Justicieae, subtribe Justiciinae. Subtribe Justiciinae is subdivided into five genera, one of them as Adhatoda, which is separated from Justicia by anther shape.
Manning & Norris (1985) treated the southern African members of Adhatoda as a separate genus. They pointed out differences between Adhatoda and Justicia in the upper corolla lip, anther theca and stipitate capsule.
