EDINBURGH JOURNAL OF BOTANY 78, Article 387: 1–17 (2021). https://doi.org/10.24823/EJB.2021.387 © the Authors under a CC BY 4.0 International Licence Published by the Royal Botanic Garden Edinburgh ISSN (online): 1474-0036, ISSN (print): 0960-4286 REVISITING THE HEDYOTIS–OLDENLANDIA COMPLEX IN INDIA, WITH A NOTE ON SCLEROMITRION M. D. Nandikar* & S. P. Bramhadande In recent years, new generic circumscriptions have been proposed in the Hedyotis–Oldenlandia complex. A comprehensive revision of Indian Hedyotis sensu lato, published in 2004, was based on a broad generic concept of the genus and does not uphold new generic delimitations. Therefore, the present article has been prepared to apply modern generic concepts to the Indian taxa. In India, 102 taxa are currently recorded under the Hedyotis–Oldenlandia complex, belonging to 12 genera (i.e. Debia, Dentella, Dimetia, Edrastima, Exallage, Hedyotis, Involucrella, Kohautia, Leptopetalum, Neanotis, Oldenlandia and Scleromitrion). The characters of these genera have been reviewed and their species enumerated, and consequently, five new combinations are proposed. Scleromitrion in India is discussed in relation to its phenotypic variation, and a key to the six recognised species is presented. Keywords. Distribution, enumeration, Hedyotis sensu lato, India, nomenclature, taxonomy. Received 31 July 2020 Accepted 19 May 2021 Published 9 December 2021 Introduction Generic delimitations within the tribes Hedyotideae Cham. & Schltdl. ex DC. and Spermacoceae Bercht. & J. Presl of the family Rubiaceae are hotly debated and regularly updated (Mabberley, 2017). A particularly difficult group is formed by a pantropical assemblage of mainly herbaceous plants: the Hedyotis–Oldenlandia complex. The complex comprises about 500–600 species (Neupane et al., 2015). In the Flora of British India, 80 taxa are recognised (Hooker, 1880) in the complex. In contrast, Dutta & Deb (2004) recognised 74 species classified in seven sections of Hedyotis sensu lato (i.e. Anotidopsis, Diplophragma, Hedyotis, Involucrella, Kohautia, Oldenlandia, Scleromitrion) in the Indian subcontinent. The various generic delimitations within the Hedyotis–Oldenlandia complex are often confusing. A widely defined genus Hedyotis, which includes Oldenlandia and several other smaller genera (Fosberg, 1943; Merrill & Metcalf, 1946; Lewis, 1961; Rogers, 1987; Wagner et al., 1989; Fosberg & Sachet, 1991; Dutta & Deb, 2004), is not supported by the results of new morphological and molecular studies (Terrell & Robinson, 2003; Groeninckx et al., 2009; Neupane et al., 2009; Guo et al., 2013; Wikström et al., 2013; Wang et al., 2014; Neupane et al., 2015; Gibbons, 2020). In this article, the species and sections of Hedyotis sensu lato recognised in India (Wight & Arnott, 1834; Bremekamp, 1952, 1974; Dutta & Deb, 2004) are critically reviewed in light of Naoroji Godrej Centre for Plant Research (NGCPR), 431 Lawkim Campus, Shirwal, Satara – 412 801, Maharashtra, India. * Corresponding author: mnandikar@gmail.com. 2 The Hedyotis–Oldenlandia complex in India new insights from these recent studies. As a result, 12 genera are recognised in India (India to world species ratio in parentheses): Debia (2:4), Dentella (1:8), Dimetia (3:6), Edrastima (1:5), Exallage (6:22), Hedyotis (33:180), Involucrella (1:2), Kohautia (4:27), Leptopetalum (2:8), Neanotis (22:34), Oldenlandia (19:190) and Scleromitrion (6:24). Additionally, five new combinations are proposed, and the generic circumscriptions of Oldenlandia and Scleromitrion are discussed. Materials and methods The Indian species in the Hedyotis–Oldenlandia complex are here reviewed based on recent insights into the generic delimitations within tribe Spermacoceae arising from the work of Kårehed et al. (2008), Groeninckx et al. (2009), Neupane et al. (2009), Guo et al. (2013), Wikström et al. (2013), Wang et al. (2014), Neupane et al. (2015) and Gibbons (2020). The Indian and worldwide distributions of the species and their morphologies are abstracted from Dutta & Deb (2004) and Plants of the World Online (POWO, 2021), and based on our field observations. Descriptive terminology is in accordance with Beentje (2016), and includes their definition of lanceolate as ‘narrowly ovate with tapering apex’. Sectional and generic notes, nomenclatural novelties, distributional notes and new species records have been gathered from published literature and floristic accounts (Wight & Arnott, 1834; Beddome, 1874; Kurz, 1877; Hooker, 1880; Gamble, 1921; Blatter, 1934; Bremekamp, 1952; Yamazaki, 1966; Rao & Hemadri, 1973; Bremekamp, 1974; Babu, 1977; Henry et al., 1979; Henry & Swaminathan, 1982; Deb & Dutta, 1983, 1985, 1986a, 1986b; Sivarajan & Biju, 1990; Ravikumar, 1999; Murugesan & Balasubramaniam, 2007; Viswanathan & Manikandan, 2008; Karuppusamy & Ravichandran, 2014; Jose et al., 2015; Soumya et al., 2017; Nandikar & Kishor, 2019; Prabhukumar et al., 2019; Kumar et al., 2020). For the plant names and authors, the International Plant Name Index (Royal Botanic Gardens, Kew, Harvard University Herbaria & Australian National Herbarium, continuously updated) has been followed throughout the text. Nomenclatural decisions have been made following the Shenzhen Code of the International Code of Nomenclature (Turland et al., 2018). The synonymisation of Hedyotis auricularia subsp. venosa (Blume) Deb (1983) is based on specimens examined at WAG and L. Other taxonomic conclusions and amendments have been reached based on the specimens at BM, E, K and P available through JSTOR Global Plants (JSTOR Global Plants, continuously updated). Photographs of living plants were taken with a Nikon D5000 DSLR camera (Nikon, Tokyo, Japan). Results and discussion The Hedyotis–Oldenlandia complex in India Although the revised enumeration of 102 Indian taxa is presented here following the modern generic classification, we found that some of the generic circumscriptions in M. D. Nandikar & S. P. Bramhadande 3 the Hedyotis–Oldenlandia complex have been not resolved satisfactorily, particularly in Oldenlandia and Scleromitrion. Because most of the genera recognised in this complex are speciose in tropical Asia, the results of more comprehensive study of Asian taxa are awaited to resolve these taxonomic ambiguities. These limitations of the generic classification are also discussed here. Debia Neupane & N.Wikstr. Debia is characterised by ovate to oblong, whorled, decurrent distal leaves; terminal cymes with elongated peduncles [often shortly pedunculate in D. andamanica (Kurz) Neupane & N.Wikstr.]; reflexed calyx and corolla; loculicidal dehiscent locules; and keeled capsules (D. andamanica) (modified from Neupane et al., 2015). It consists of four species, mainly distributed in tropical Asia, and is represented in India by two species. The Indian species were previously part of Hedyotis sect. Anotidopsis Hook.f. and Hedyotis sect. Oldenlandia (L.) Wight & Arn. Section Anotidopsis is recognised based on terminal capitate to subcapitate, pedunculate cymes; narrowly winged capsules; and recurved calyx teeth (Dutta & Deb, 2004). It previously comprised two species: Hedyotis brunonis Merr. and H. andamanica Kurz. The latter is now recognised as Debia andamanica (Figure 1A), and the former is now doubtfully placed in the genus Oldenlandia. Hedyotis ovatifolia Cav., previously grouped in section Oldenlandia, is now known as Debia ovatifolia (Cav.) Neupane & N.Wikstr. Debia andamanica is endemic to the Andaman and Nicobar Islands, India, and D. ovatifolia is known from Myanmar. Both species can be recognised by their ovate, whorled leaves and terminal cymes. However, reflexed corolla lobes (Neupane et al., 2015) are inconsistent for the circumscription of the genus Debia, because they are absent in D. ovatifolia. Dentella J.R.Forst & G.Forst This genus is characterised by its strictly pentamerous, solitary flowers; subdentate corolla lobes; and indehiscent dry capsules. Dentella is more speciose in Australia (six species, all endemic); the remaining two species occur in Asia. Dentella concinna Airy Shaw is a poorly known Malaysian species. Dentella repens J.R.Forst & G.Forst (Figure 1B) occurs throughout tropical Asia and is naturalised in other places (e.g. Madagascar: Razafimandimbison & Manjato, 2019). The Indian populations of Dentella repens are often considered as a variety, namely D. repens var. serpyllifolia (Wall. ex Craib) Verdc., due to their glabrous capsules. Because it is so widespread, a certain amount of variation in capsule hairs (densely to sparsely hairy to glabrous; Cook, 1996) should be expected, and much, if not all, of this variation would not be of taxonomic significance. Therefore, we uphold the Indian populations as Dentella repens. 4 The Hedyotis–Oldenlandia complex in India Figure 1. Field photographs. A, Debia andamanica (Kurz) Neupane & N.Wikstr.; B, Dentella repens J.R.Forst & G.Forst; C, Dimetia capitellata (Wall. ex G.Don) Neupane & N.Wikstr.; D, Exallage paradoxa (Kurz) Bremek. Photographs: A, Mayur Nandikar; B, Dinesh Valke; C, Reuben C. J. Lim; D, K. C. Kishor. M. D. Nandikar & S. P. Bramhadande 5 Dimetia (Wight & Arn.) Meisn. Dimetia can be identified by its climbing or scandent habit, capsule exserted beyond the calyx lobes, septicidal dehiscence and narrowly winged seeds. About six species are distributed in tropical Asia. Three taxa, namely Dimetia capitellata (Wall. ex G.Don) Neupane & N.Wikstr. (Figure 1C), D. capitellata var. subpubescens (Kurz) Nandikar, comb. nov. [basionym: Hedyotis capitellata var. subpubescens Kurz, J. Asiat. Soc. Bengal 46(2): 135 (1877)] and D. scandens (Roxb.) R.J.Wang, are found in Northeast India. In an Indian context, Dimetia has been treated under Hedyotis sect. Diplophragma Wight & Arn. (Dutta & Deb, 2004), which has similarities with the present circumscriptions of Hedyotis sensu stricto and Exallage. However, Hedyotis sensu stricto differs from Dimetia in having the capsule included within the calyx lobes, and Exallage differs in having an indehiscent capsule. Edrastima Raf. This genus is represented by characters such as a glabrous corolla tube and distinctly beaked capsule. It is distributed throughout the tropics and subtropics. Of a total of five species, three are found in tropical Africa and one in America; Edrastima trinervia (Retz.) Neupane & N.Wikstr. is recognised in tropical Asia. Edrastima was previously part of Hedyotis sect. Involucrella Hook.f. (Dutta & Deb, 2004). However, Edrastima trinervia (synonyms: Hedyotis trinervia Roem. & Schult., Oldenlandia trinervia Retz.) is recognised as distinct due to its glabrous corolla tube. The generic key character of a ‘distinctly beaked capsule’ as recognised by Neupane et al. (2004, 2015) has been found to be inconsistent, because in Edrastima trinervia the capsule apex does not protrude from the calyx and is obtuse. Exallage Bremek. Exallage has often been grouped as part of Hedyotis sect. Euhedyotis Wight & Arn. (1834) (syn. section Hedyotis L. auct. Dutta & Deb, 2004). However, it can be separated from the other species in the Hedyotis–Oldenlandia complex by its axillary inflorescence and its crustaceous, hard, indehiscent, globose fruits with tumescent apices (Bremekamp, 1952; Neupane et al., 2015; Nandikar & Kishor, 2019). About 22 species are distributed in tropical Asia, mainly in Southeast Asia. Six taxa are represented in India, namely Exallage auricularia (L.) Bremek. [including Hedyotis auricularia L. subsp. venosa (Blume) Deb, syn. nov.], E. cristata (Willd. ex Roem. & Schult.) Nandikar & K.C.Kishor, E. fulva (Hook.f.) Neupane & N.Wikstr., E. insularis (Spreng.) Neupane & N.Wikstr., E. paradoxa (Kurz) Bremek. (Figure 1D) and E. ulmifolia (Wall.) Bremek. All these also occur in Southeast Asia, except for Exallage paradoxa, which is endemic to the Andaman Islands, India. Hedyotis auricularia subsp. venosa has been found to be 6 The Hedyotis–Oldenlandia complex in India conspecific, because leaves in H. auricularia L. are consistently broadly elliptic-lanceolate and 3- to 7-nerved. Hedyotis L. sensu stricto Hedyotis is a genus of perennial herbs, shrubs and small trees characterised by a pubescent corolla throat, included capsule apex, and septicidally, late-dehiscing capsules (modified from Dutta & Deb, 2004; Neupane et al., 2015). Other characters, such as those of the stipule, leaf (shape, size and venation) and inflorescence, are extremely variable. Often, seeds are ridged and winged (characters also known in Dimetia). About 180 species of Hedyotis sensu stricto are distributed in tropical Asia and the Pacific Northwest, with 33 species represented in India. Tamil Nadu and Kerala States are home to Hedyotis albonerva Bedd., H. articularis R.Br. ex Wight & Arn., H. articularis subsp. santapaui (Shetty & Vivek.) Deb & Ratna Dutta, H. barberi (Gamble) A.N.Henry & Subr., H. beddomei Hook.f., H. buxifolia Bedd., H. devicolamensis Deb & Ratna Dutta, H. eualata (Gamble) A.N.Henry & Subr., H. eualata var. agastyamalayana A.N.Henry & Subr., H. gamblei A.N.Henry & Subr., H. hirsutissima Bedd., H. leschenaultiana DC., H. leschenaultiana var. wynaadensis (Gamble) Deb & Ratna Dutta, H. pruinosa Wight & Arn., H. purpurascens Hook.f., H. ramarowii (Gamble) R.S.Rao & Hemadri, H. swertioides Hook.f., H. travancorica Bedd. and H. verticillaris Wight & Arn. Hedyotis membranacea Thwaites, H. trimenii Deb & Ratna Dutta and H. viscida Bedd. occur in the Western Ghats of Sri Lanka, whereas H. fruticosa L., H. tetrandra (Roxb.) Craib and H. uncinella Hook. & Arn. (Figure 2A) are distributed in eastern India and Southeast Asia. Hedyotis congesta R.Br. ex G.Don is distributed in the Andaman Islands and Malaysia (Nandikar & Kishor, 2019). Its resemblance to Hedyotis prostrata Blume remains doubtful (Nandikar & Kishor, 2019). Neighbouring Sri Lanka is more speciose, having c.27 endemic taxa compared with c.26 taxa endemic to peninsular India. Section Diplophragma Wight & Arn. (1834) is now included within the new generic circumscription of Hedyotis sensu stricto in India. Since the latest revision of Hedyotis sensu lato (Deb & Dutta, 2004), seven new species, namely H. indirae K.M.P.Kumar & Aiswarya, H. kottangathattiensis M.B.Viswan. & Manik., H. nairii Murug. & V. Balas., H. rajasekaranii Karupp. & V.Ravich., H. shettyi K.Ravik. & V.Lakshm., H. shoolamudiana Sunil, Naveen Kum. & K.M.P.Kumar (as ‘shoolamudianus’) and H. sithiravaraiensis Muruganand., Devanath., S.Ravik. & D.Naras., have been described (Ravikumar, 1999; Murugesan & Balasubramaniam, 2007; Viswanathan & Manikandan, 2008; Karuppusamy & Ravichandran, 2014; Prabhukumar et al., 2019; Kumar et al., 2020; Muruganandam et al., 2020), mainly from the southern Western Ghats of Tamil Nadu and Kerala. M. D. Nandikar & S. P. Bramhadande 7 Figure 2. Field photographs. A, Hedyotis uncinella Hook. & Arn.; B, Leptopetalum biflorum (L.) Neupane & N.Wikstr.; C, Neanotis foetida (Hook.f.) W.H.Lewis; D, Neanotis tubulosa (G.Don) Mabb.; E and F, Kohautia aspera (Heyne ex Roth) Bremek. Photographs: A, Nidhan Singh; B–F, Mayur Nandikar. 8 The Hedyotis–Oldenlandia complex in India Involucrella (Benth. & Hook.f.) Neupane & N.Wikstr. This genus is characterised by terminal capitate cymes amid involucre-like distal leaves, and membranous, irregularly dehiscing capsules. Two species are found in Asia (Neupane et al., 2015). Involucrella coronaria (Kurz) Neupane & N.Wikstr. (syn. Hedyotis merguensis Hook.f.) is distributed in Mizoram and Tripura States in India (Dutta & Deb, 2004). Kohautia Cham. & Schltdl. Kohautia can be recognised by its weak habit, brevistylous or longistylous flowers (stigma positioned below or above the anthers), and slender corolla tube with included stamens. Walpers (1843) grouped the Kohautia species into Hedyotis sect. Kohautia; however, the recent generic circumscription upheld the genus Kohautia, with 27 species distributed from Africa to Australia (Neupane et al., 2015). Four species, namely Kohautia aspera (Heyne ex Roth) Bremek. (Figure 2E,F), K. coccinea Royle, K. gracilis (Wall.) DC. and K. retrorsa (Boiss.) Bremek., are distributed in the Indian subcontinent and the Arabian Peninsula. Kohautia nagporensis (Brace ex Haines) Santapau & Merch. is the only Indian endemic and is reported from central India, Gujarat State and Maharashtra State. Leptopetalum Hook. & Arn. Members of this genus were previously grouped in section Oldenlandia (L.) Wight & Arn. and genus Thecagonum Babu [excluding T. ovatifolium (Cav.) Babu (= Debia ovatifolia)]. However, the species with a glabrous habit, winged, loculicidal dehiscing capsules, and pitted seeds have now been retained in Leptopetalum (Neupane et al., 2015). The genus consists of eight species distributed mainly in tropical Asia. Two species are represented in India, namely Leptopetalum biflorum (L.) Neupane & N.Wikstr. (syn. Hedyotis hermanniana Ratna Dutta) (Figure 2B) and L. pteritum (Blume) Neupane & N.Wikstr., these being found in Southeast Asia, India and the Andaman Islands (Nandikar & Kishor, 2019). Neanotis W.H.Lewis Neanotis is recognised by characters such as its annual, herbaceous habit and pluriaperturate (6–12 apertures), coarsely reticulate pollen (Lewis, 1966; Neupane et al., 2015). Characters including a fetid odour and peltate to planoconvex seeds with a distinct cavity can also be used to distinguish Neanotis from its allied genera. About 34 species are distributed in tropical Asia to Australia, with 22 represented in India (POWO, 2021; WCVP, 2021). Of these, Neanotis carnosa (Dalzell) W.H.Lewis, N. decipiens (Hook.f.) W.H.Lewis, N. foetida (Hook.f.) W.H.Lewis (Figure 2C), N. indica (DC.) W.H.Lewis, N. lancifolia (Hook.f.) W.H.Lewis, N. latifolia Deb & Ratna Dutta, N. longiflora W.H.Lewis, N. montholonii (Hook.f.) W.H.Lewis, N. prainiana (Talbot) W.H.Lewis, N. rheedei (Wall. ex Wight & M. D. Nandikar & S. P. Bramhadande 9 Arn.) W.H.Lewis, N. ritchiei (Hook.f.) W.H.Lewis and N. sahyadrica Billore & S.K.Mudaliar are endemic to peninsular India. Neanotis calycina (Wall. ex Hook.f.) W.H.Lewis, N. gracilis (Hook.f.) W.H.Lewis, N. ingrata (Wall. ex Hook.f.) W.H.Lewis, N. oxyphylla (Wall. ex D.Don) W.H.Lewis, N. rhombicarpa T.Yamaz. and N. urophylla (Wall. ex Wight & Arn.) W.H.Lewis are distributed in the eastern and northeastern regions of India to Nepal and Bangladesh. Neanotis monosperma (Wall. ex Wight & Arn.) W.H.Lewis and N. tubulosa (G.Don) Mabb. [syn. N. quadrilocularis (Thwaites) W.H.Lewis] (Figure 2D) appear to be endemic to the Western Ghats of India and Sri Lanka. However, the latter species is doubtfully known from Thailand (Garrett 389 [TCD0017371]). Neanotis hirsuta (L.f.) W.H.Lewis and N. wightiana (Wall. ex Wight & Arn.) W.H.Lewis are distributed from India to China. Until Lewis (1966) described the genus Neanotis, the species were partly grouped in the section Anotis Wight & Arn. (1834). However, some were classified under the genera Hedyotis, Oldenlandia and Putoria Pers. It remains difficult to differentiate some Oldenlandia species from Neanotis, due to the limited number of qualitative characters. Oldenlandia L. sensu stricto This ill-defined genus in the Hedyotis–Oldenlandia complex comprises about 190 species distributed in the Old World tropics and shares many similarities with Scleromitrion (Guo et al., 2013; Wang et al., 2014; Neupane et al., 2015). Circumscription of the morphological characters and their similarities with those of allied genera makes Oldenlandia taxonomically challenging, and therefore it is difficult to estimate the number of species. In an Indian context, to circumscribe Oldenlandia we have used a combination of characters such as linearlanceolate leaves; solitary to many-flowered, pedunculate cymes; usually inserted stamens; and loculicidally dehiscent capsules. These characters are artificial and are used here to define the genus in India, mainly represented by section Oldenlandia sensu Dutta & Deb (2004). They may or may not be applicable to Oldenlandia species outside the Indian subcontinent. Nineteen taxa are reported from India, namely Oldenlandia affinis (Roem. & Schult.) DC., O. attenuata (Willd.) M.R.Almeida, O. corymbosa L., O. corymbosa var. linearis (DC.) Verdc., O. dineshii Sojan & V.Suresh, O. graminicola (Kurz) Deb & M.Gangop., O. herbacea (L.) Roxb., O. hygrophila Bremek., O. monocephala Kuntze, O. paniculata L., O. pseudocorymbosa (Bakh.f.) Raizada, O. pumila (L.f.) DC., O. smitacrishnae Nandikar & K.C.Kishor, O. stricta L., O. stricta subsp. arenaria (Haines) Nandikar, comb. nov. [basionym: O. arenaria Haines, J. Asia. Soc. Bengal Ser. 2(15): 315 (1920); endemic to Odisha], O. stricta var. shuteri (Hook.f.) Nandikar, comb. nov. [basionym: O. shuteri Hook.f., Fl. Brit. India 3: 69 (1880); Deb & Dutta (1985); endemic to Tamil Nadu and Andhra Pradesh], O. umbellata L. [syn. Hedyotis puberula (G.Don) Arn.] (Figure 3B–D), O. vasudevanii M.Soumya & Maya (doubtfully distinct from O. stocksii Hook.f.) and O. wallichii Craib. Of these, Oldenlandia graminicola and O. smitacrishnae are endemic to the Andaman Islands, and all others except O. monocephala are endemic to Kerala. 10 The Hedyotis–Oldenlandia complex in India Figure 3. Field photographs. A, Oldenlandia stocksii Hook.f. B–D, Oldenlandia umbellata L.: B, habit; C, brevistylous flower; D, longistylous flower. Photographs: Mayur Nandikar. M. D. Nandikar & S. P. Bramhadande 11 Ill-defined taxa in Scleromitrion The Scleromitrion clade identified by Neupane et al. (2015) and Gibbons (2020) included distinctly paniculate, corymbose species (Hedyotis diffusa Willd., Hedyotis scabra Wall. ex Kurz and Oldenlandia linoides Griff., and many other Southeast Asian taxa) that have been popularly recognised in India under Hedyotis and Oldenlandia. The endemic Indian species Oldenlandia stocksii Hook.f. (endemic to Goa, Karnataka and Maharashtra), known for its axillary, solitary to terminal 2-flowered cymes (Figure 3A), is also nested in Scleromitrion. However, difficulties remain regarding the phenotypic distinctness of Scleromitrion from its most closely related genera. We believe that the taxa with terminal and axillary, paniculate or corymbose or simple cymes with pedicellate, often heterostylous flowers with distinctly exserted stamens deserve to be recognised in a distinct genus rather than in Scleromitrion. However, a comprehensive morphological and molecular study throughout the distribution range would be required for their resolution, and therefore we consider them to be of uncertain generic placement. Scleromitrion (Wight & Arn.) Meisn. Scleromitrion has been reinstated in recent years (Guo et al., 2013; Wang et al., 2014; Neupane et al., 2015; Gibbons, 2020). It is characterised by its axillary cymes of subsessile, homostylous flowers, and erect, rigid calyx lobes, converging to the apex in the capsule (Wight & Arnott, 1834; Neupane et al., 2015). Most Indian species of Scleromitrion are reported to have a hairy corolla throat [S. brachypodum (DC.) T.C.Hsu being an exception], but this is not a constant character of the genus, as reported by Gibbons (2020) for the Australian taxa. The genus comprises 24 species distributed in tropical Asia and Australia (Gibbons, 2020; POWO, 2021). In India, six species are represented in Scleromitrion, namely S. angustifolium (Cham. & Schltdl.) Benth., S. brachypodum (DC.) T.C.Hsu, S. cyananthum (Kurz) Nandikar, comb. nov. [basionym: Hedyotis cyanantha Kurz, J. Asiat. Soc. Bengal, Pt 2, Nat. Hist. 45(2): 136 (1876)], S. neesianum (Arn.) Nandikar, comb. nov. [basionym: Hedyotis neesiana Arn., Nova Acta Acad. Caes. Leop.-Carol. German. Nat. Cur. 18: 341 (1836); heterotypic synonym: Scleromitrion nitidum Kurz] (Figure 4A), S. pinifolium (Wall. ex G.Don) R.J.Wang and S. verticillatum (L.) R.J.Wang (Wight & Arnott, 1834; Walpers, 1843; Dutta & Deb, 2004; Hsu & Chen, 2017). The Indian taxa can be recognised by their herbaceous habit; axillary, 1to 6-flowered cymes with sessile to subsessile flowers (rarely terminal capitate cymes in Scleromitrion cyananthum and S. pinifolium); exserted stamens and style; and ovoid crustaceous capsules with converging, erect, rigid calyx teeth. Scleromitrion brachypodum (Figure 4B–D) is often considered conspecific with Hedyotis diffusa (Roxburgh, 1820; Dutta & Deb, 2004; Rao et al., 2019; WCVP, 2021). However, it is 12 The Hedyotis–Oldenlandia complex in India Figure 4. Field photographs. A, Scleromitrion neesianum (Arn.) Nandikar. B–D, Scleromitrion brachypodum (DC.) T.C.Hsu: B, habit; C, flower; D, capsule. Photographs: Mayur Nandikar. M. D. Nandikar & S. P. Bramhadande 13 quite different from Hedyotis diffusa in having linear leaves, 1- or 2-flowered axillary sessile to subsessile cymes, urceolate flowers and larger fruits (modified from Sivarajan & Biju, 1990). It is a common species in wet lowlands and cultivated fields, and is distributed across the Asian subcontinent. One of our collections of Scleromitrion brachypodum from Amboli, Maharashtra (Nandikar & Bramhadande 002480 [NGCPR]) has sessile flowers and rigid calyx lobes, which clearly support the opinion of Hsu & Chen (2017) in recognising it in Scleromitrion. An identification key to all reported species of Scleromitrion sensu stricto (species with sessile to subsessile, homostylous flowers and erect, rigid calyx lobes) in India is presented below. Key to the species of Scleromitrion sensu stricto in India 1a. 1b. Leaves linear, or narrowly elliptic; corolla tube pubescent within ____________________ 2 Leaves setaceous, linear, or elliptic or elliptic-lanceolate; corolla tube glabrous within __ 3 2a. 2b. Stem terete, glabrous; cymes axillary, 3- to 6-flowered ________________ S. angustifolium Stem angular, sparsely hispid; cymes axillary and terminal, 5- to 15-flowered S. pinifolium 3a. 3b. Leaf apex bristle pointed; flowers blue in axillary and terminal in leafy cymes S. cyananthum Leaf apex acute or obtuse; flowers white in axillary, capitate cymes _________________ 4 4a. 4b. Stipule cupular; filaments 4–4.6 mm long; capsule hispid ______________ S. verticillatum Stipule deltate; filaments 1–2 mm long; capsule glabrous __________________________ 5 5a. Stem angular, often grooved; leaves elliptic, 30–60 × 0.5–20 mm, rounded to subcordate at base; cymes 2- to many-flowered; corolla lobes spreading ____________ S. neesianum Stem terete; leaves linear or narrowly elliptic, 25–35 × 0.2–0.5 mm, cuneate to attenuate at base; cymes 1- to 2-flowered; corolla urceolate __________ S. brachypodum 5b Acknowledgements The authors are grateful to Vijay M. Crishna, Director of the Naoroji Godrej Centre for Plant Research (NGCPR), for his constant support and encouragement, and to Mitta Mahendra Nath (Sri Venkateswara University, Tirupati) and K. C. Kishor (NGCPR) for their assistance in the field. We thank herbarium staff at BM, BSI, E, K, L, P and WAG for permission to examine herbarium specimens and for making these available through their webpages and JSTOR. 14 The Hedyotis–Oldenlandia complex in India ORCID iDs https://orcid.org/0000-0001-8626-3669 M. D. Nandikar S. P. 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