Chamaecrista rigidifolia ( Bentham 1870: 142 ) Irwin & Barneby (1982: 655)

Mendes, Thainara Policarpo, Souza, Alessandro Oliveira De & Silva, Marcos José Da, 2021, Taxonomic review of Chamaecrista sect. Absus subsect. Absus ser. Paniculatae (Benth.) H. S. Irwin & Barneby (Leguminosae, Caesalpinioideae), Phytotaxa 495 (1), pp. 1-64 : 46-52

9. Chamaecrista rigidifolia ( Bentham 1870: 142) Irwin & Barneby (1982: 655) . ≡ Cassia rigidifolia Bentham (1870: 142) . Type: — BRAZIL. Mato Grosso: Chapada Dos Guimarães, NE, of Cuiabá, V.1827, Riedel 482/960 (lectotype: LE! [00002375], designated here; isolectotypes: K! [K000555592], photo IPA! [IPA1048], NY! [NY 1497]; LE! [LE00002376, LE00002377], US [00001682]). Figs. 28 and 29

Cassia poiretioides Hoehne (1922: 186) . Type: — BRAZIL. MATO GROSSO: entre Vilhena e Amarante , Rondônia, Mato Grosso, V.1918. fl., Kulhman 2031 = Comiss. Linh. Telegre 2031 (lectotype: SP! [000893], designated here; isolectotype: R! [000027430] e RB! [00538465]) .

Shrubs 0.80–4 m tall, erect or pendent, cespitose, branched or not. Stem and branches waxy and glabrous, stem and adult branches brown, stem and young branches pinkish. Stipules 1.5–1.6 mm long, lanceolate, persistent. Leaves 4.4–7.2 cm long, regularly distributed throughout the branches, ascending; pulvinus 3–7 mm long, conspicuously dilated, not striated; petiole 2.9–5.3 cm long, thin, cylindrical and sulcate above; rachis 4–5.8 cm long, cylindrical and sulcate above; interfoliolar segments 1.7–2.2 cm long; pulvinule 1–3.5 mm long, visibly dilated; leaflets 2–5 pairs, coriaceous; blades 2.8–5.8 × 1.9–5.6 cm, ovate, oval-elliptic or elliptic, margin entire, plane, glabrous, surface abaxial and adaxial glabrous, base asymmetrically cordate or asymmetrically rounded, apex obtuse, sometimes emarginated, with mucron or not, dark green, opaque. venation brochidodromous, secondary veins 8–11 pairs, green. Panicles 18–32 cm long, with 3–10 secondary axis, geminate, terminal or axillary, with flowers laxly distributed, slightly pendent, glabrous, exserted from the foliage. Bracts 1–1.2 × 0.2–0.9 mm, triangular, margin entire, yellowish, pubescent, persistent. Bracteoles 1–2.2 × 0.2–0.4 cm, oblong-lanceolate, apex acute, margin entire and ciliate, light green, caduceus. Buds 1–1.2 cm long, ovoid or orbicular, green-yellowish, glabrous, apex obtuse. Flowers 3.7–5.1 cm long; pedicel 1.2–4.2 cm long, robust, cylindrical; sepals 1–1.3 × 0.6–0.9 cm, elliptic, apex obtuse or acute, yellow with purplish pigmentation; glabrous; petals 1.1–3.5 × 0.8–3 cm, obovate, light yellow, with the adaxial petal like a standard, one of the inner petals coiled in the androecium; stamens 5–9 mm long, filaments ca. 1mm long; anthers 4– 8 mm long, not mucronulate at apex. Ovary 0.2–0.6 × 1–1.1 cm, glabrous, styles 1.2–1.8 cm long, glabrous. Legume 3.5–4.5 × 0.5–0.8 cm, glabrous, narrow-oblong, green with purplish pigmentation to brown. Seeds 5–6 × 3.1–4 mm, orbicular, dark brown, smooth, glossy.

Representative specimens examined: — BRAZIL. Mato Grosso: Barra do Garças , NE of Barra do Garça, 500 m, 4 May 1973, (fl.), W . R . Anderson 9683 ( NY, UB); Parque Estadual da Serra Azul, estrada de acesso ao mirante do Cristo , logo após a entrada que leva às cachoeiras, 24 March 2016, T . P . Mendes, J . A . Oliveira & R . C . Sodré 31 ( UFG); ib., Serra Azul, ca. 100 metros da entrada para a trilha da Cachoeira da Usina , 15°52’29’’S, 52°15’7’’W, 396 m, 24 March 2016, T . P . Mendes, J . A . Oliveira & R . C . Sodré 32 ( UFG), 33 ( UFG), 34 ( UFG); ib., 27 September 2016, (fl., fr.), T . P . Mendes, J . A . Oliveira, A . O . Souza 355 ( UFG), 356 ( UFG); Chapada dos Guimarães, sandstone cliffs and adjacente cerrados and campos at western edge of the Chapada dos Guimarães, 550–680m, 13 February 1975, William R . Anderson 11362 ( NY); ib., Parque Estadual Chapada dos Guimarães, estacionamento da Cidade de Pedras , 15°17’59’’S, 55°50’45’’W, 681m, 25 March 2016, (fl.), T . P . Mendes, J . A . Oliveira & R . C . Sodré 42 ( UFG), 43 ( UFG), 44 ( UFG), 45 ( UFG), 46 ( UFG); ib., Trilha para a Cachoeira do Pulo , circuito das cachoeiras, 15°24’31’’S, 55°49’52’’W, 603m, 26 March 2016, (fl., fr.), T . P . Mendes, J . A . Oliveira & R . C . Sodré 47 ( UFG), 48 ( UFG); ib., estrada para a casa de pedras, 15°25’30’’S, 55°49’60’’W, 671 m, 27 March 2016, (fl.), T . P . Mendes, J . A . Oliveira & R . C . Sodré 49, 50 ( UFG); General Carneiro, margem direita do km 129 da BR-070, de General Carneiro ao Povoado de Paredão Grande, depois da entrada das aldeias Eruquel e Nebure , 15°35’4’’S, 53°11’24’’W, 511 m, 25 March 2016, T . P . Mendes, J . A . Oliveira & R . C . Sodré 36 ( UFG), 37 ( UFG), 38 ( UFG), 39 ( UFG), 40 ( UFG); Pedra Preta, Rod. BR- 364, Serra da Petrovina , 16 May 1995, (fl.), G . Hatschbach et al. 62843 ( MBM, NY); São José do Rio Claro, Fazenda Cachoeira de Pau , 13°52’S, 56°32’’ W , 14 June 1997, (fl.), V . C . Souza et al. 18124 ( ESA); Rio Verde, Rod. Campo Grande-Cuiabá , 15 May 1973, G . Hatschbach 31960 ( NY, MBM); Xavantina, Drainage of the upper Rio Araguaia , ca. 30 km S of Xavantina, 400m, 11 June 1966, (fl.), H . S Irwin et al. 16916 ( NY, UB); ib., Serra do Roncador, Rio Turvo, ca. 210 Km N of Xavantina, 500 m, H . S . Irwin et al. 17239 ( NY, UB) . Mato Grosso do Sul: Chapadão do Sul, Fazenda Ribeirão, entrada do Km 130, rodovia MS-306, 18°48’41’’S, 52°52’48’’W, 800 m, 31 May 2001, (fl., fr.), A . Pott et al. 9008 ( CGMS). Costa Rica, balneário do município, 18°31’57.9”S, 53°07’27.4”W, 27 June 2001, A . L . B. Sartori et al. 620 ( CGMS). Minas Gerais: Chapada Gaúcha, Serra das Araras, Cerrado da capelinha, Parque Estadual Serra das Araras, 11 November 2003, Martins, RC, & Gomes, B . M . 449 ( UB). BOLÍVIA: Santa Cruz. Província de Chiquitos. South slope of the Serrania de Santiago, 5–10 km east of town of Santiago de Chiquitos , 18°23’S, 59°30’W, 850–900 m, 20 July 1983, (fl.), D. C . Daly et al. 2142 ( NY); ib., Serrania de Santiago , 3 km N of Santiago de Chiquitos, 18°20’S, 59°40’W, 900 m, 15 October 1986, (fl.), Tim Killeen 2806 ( F, NY) ;

Distribution and ecology: —Species registered for Bolivia and Brazil. In the latter country, it was cited by the Rando et al. (2020) for Goiás, Mato Grosso, Mato Grosso do Sul and Rondônia, and, therefore, is being referred to Minas Gerais in this study (Fig. 36A). It growsin in cerrados típicos, cerrados densos, cerrado ralos and cerrados rupestres, campos sujos and campos rupestres, edge of gallery forests, in flat areas, hillsides or hilltops, forming aggregate populations. In its areas of occurrence, the altitude varies from 400–1280 meters, although most individuals are around 800 meters.

Flowering and fruiting: —Collected with flowers and fruits in March and November.

Etymology: —The specific epithet “ rigidifolia ” refers to the rigid leaflets of the species.

Conservation status: —Due to its occurrence in an area of occurrence greater than 390,000 km 2, to be collected in more than 10 locations, and to present populations with more than 40 individuals, Chamaecrista rigidifolia has its conservation considered as Least Concern (LC).

Typification: — Cassia rigidifolia was described by Bentham (1870) in Flora Brasiliensis based on a collection by “Riedel s.n” whose label of the exsiccate was written only “ In locis saxosis Serra da Chapada ”. Irwin & Barneby (1978) indicated the “Riedel 482” and “Riedel 960” collections belonging to the herbarium as the species holotype. During this study, we found that the collections indicated by the latter authors correspond to the same collection mentioned by Bentham (1840) for the equality of information contained on the labels of their exsiccates. We also verified that there is doubt as to the correct number of the species collector, since the collection presents two numbers for the same individual. In the face of such dubiousness and considering that a holotype cannot be represented by equal collections with different numbers and the fact that at Herbarium L there is more than one duplicate of the collection indicated by the number “Riedel 960”. We chose to lectotify the species, and, for consequently, as its lectotype, the collection belonging to the herbarium L under Barcode L00002375 (Fig. 30) which is the only one among the collections that is fertile.

Cassia poiretioides Hoehne (1922: 186) was described by Hoehne in 1922 in the work “Commission of Strategic Telegraphic Lines from Mato Grosso to Amazonas ”, which indicated the Kulhmann 2031 collection collected between Vilhena and Amarante, state of Mato Grosso, as typus. Irwin & Barneby (1978) proposed Cassia poiretioides as a synonym for Cassia rigidifolia given the vegetative and reproductive similarities between species. Four years later, these same authors ( Irwin & Barneby 1982) transferred Cassia rigidifolia to the genus Chamaecrista (= Ch. rigidifolia ). Analyzing the typus and protologues collections of the two taxa, we agree with all the decisions made by Irwin & Barneby (1982). In this same work, the authors indicated the Kulhmann 7635 = Comiss as typus by C. poiretioides . Linh. Telegram. 2031. Consulting the original work of the species (Hoehne 1940) we find that the type collection of the same is Kulhmann 7635 = Comiss. Linh. Telegram. 2031. As the latter is deposited in the R and RB herbariums, we have chosen to consider the Kulhmann 2031 sample of the Herbarium SP (SP 000893) as its lectototype (Fig. 31) because it reflects the original description of the species, being in good condition conservation and own flowers.

Morphological relationships and characterization: —Irwin & Barneby, in 1978, in studies carried out on Cassia recognized two varieties for the species: Ch. rigidifolia var. rigidifolia and Ch. rigidifolia var. veadeirana , differentiated mainly by the first ones having oblong-elliptical leaflets (vs. obovals or suborbiculars in Ch. veadeirana var veadeirana ), inflorescence axis and glabrous buds (vs. setulose), pubescent bracts and ciliate bracts (vs. both setulose and pubescent).

Recently, Mendes et al. (2020) in a phylogenetic study aimed at Ch. ser. Paniculatae recognized the two varieties proposed by Irwin & Barneby (1982) for Ch. rigidifolia as distinct species, a decision supported also by the morphological discontinuity presented by both species. Cota et al. (2020) synonymized Ch. rigidifolia sensu Mendes et al. (2020) under Ch. claussenii stating that the species were not morphologically compared by Mendes et al. (2020). After studying several herborized materials and field observations, as, we noticed that, despite the morphological similarities, Ch. rigidifolia is a distinct species from Ch. claussenii because they present a set of characters that differentiate them, as already discussed in the comments of the latter.

Chamaecrista rigidifolia can be recognized mainly by its waxy branches and axis of inflorescence, dense leaves with elliptical or oblong-elliptical leaflets with geminate secondary axis. The species also resembles Ch. veadeirana in that it shares the shrubby habit, waxy stem, leaves regularly distributed throughout the plant and ascendants and ovoid buds, but differs from this in that it presents dense leaves in Ch. rigidifolia (vs. sparse leaves), small petiole (vs. robust), oval leaflets (vs. oboval or elliptical-oboval) with obtuse apex (vs. rounded) and corded asymmetric base (vs. asymmetric-obtuse), with greenish margin and veins (vs. vinaceous), impressed tertiary veins (vs. prominent), panicles up to 32 cm long. (vs. up to 78 cm long), in addition to the secondary axis of inflorescence, buds, the outer face of the sepals and glabrous fruits (vs. setulose), elliptical sepals with up to 0.9 cm long (vs. lanceolate up to 1.7 cm long) and light yellow petals (vs. dark yellow).