Chamaecrista mimosoides

Musandiwa, Liada, Magee, Anthony R. & Boatwright, James S., 2022, A Taxonomic Revision of Chamaecrista (Caesalpinioideae, Cassieae, Cassiinae) in Southern Africa, Systematic Botany (Basel, Switzerland) 47 (4), pp. 992-1011 : 1006-1008

9. CHAMAECRISTA MIMOSOIDES (L.) Green , Pittonia 4 (20): 27 (1899);

Brummitt in Fl. Zambesiaca 3(2): 136 (2007). Cassia mimosoides L. Sp. Pl. : 379 (1753); Oliver in F. T.A. 2: 280 (1871); Baker, Legum. Trop. Afr.: 642 (1930); Steyaert in F. C.B. 3: 514 (1952); Mendonça & Torre in C.F.A. 2: 181 (1956); Keay in F.W.T.A., ed.2, 1: 453 (1958); Brenan in F.T.E.A., Legum.-Caesalp.: 100 (1967); Ross, Fl. Natal: 195 (1973); Gordon-Gray in F.S.A. 16(2): 104 (1977).

TYPE: SRI LANKA. Zeylona, without date, Hermann 154 (lectotype: BM [ BM-000594576 ]–image!, designated by Larsen et al. 1980).

Annual herbs to 0.8 m high. Stems prostrate or decumbent, branching from the ground becoming rounded, with appressed short curved hairs. Leaves paripinnate, 30–85 × 2–7 mm, slightly tapering distally; stipules, 4–9 mm long, triangular, base oblique, apex acuminate; extrafloral nectaries at or near top of petiole, small, ± 0.5 mm long, sessile, rounded; rachis crested. Leaflets 23–62-jugate, base oblique, apex mucronate; margin ciliate. Inflorescence supra-axillary, 1(2) flowered; flowers 3–6 × 3–5; bract with short curved hairs, base oblique, apex accumulate; bracteoles 2, glabrous, towards the top of pedicel. Pedicels with short appressed or sometimes with long straight hairs, at flowering 3–8 mm long, at fruiting 6–10 mm long. Sepals 5, lanceolate, 4–6 × 1–3 mm, with short curved hairs. Petals obovate, 4–8 mm. Stamens 9–10, slightly curved, flattened, anthers in three series, 2(3) small 2–3 mm long, 4 medium ± 4 mm long, 4 large ± 5 mm long, filaments short (1–2 mm long). Ovary densely covered with greyish to whitish hairs, style curved, glabrous. Pods straight or slightly curved, 35–60 × 3–4 mm, flattened, with appressed hairs. Seeds not seen.

Diagnostic Characters — Chamaecrista mimosoides can be confused with C. grandiglandulata and C. gordon-grayei with which it shares a crested rachis, but can be distinguished from those species by its low growth form, and small, circular or circular-elliptic extrafloral nectaries on the petiole ( Fig. 3G ).

Distribution and Ecology — Chamaecrista mimosoides is widespread in tropical Africa and southern Asia ( Gordon-Gray 1977; Brummitt et al. 2007). In southern Africa, C. mimosoides is widespread from Lydenburg in Mpumalanga, through Vryheid and Stanger in Kwa-Zulu Natal, to Port St. Johns in the Eastern Cape extending across to Mbabane in Swaziland ( Eswatini) ( Fig. 14 ), growing in grassland in shallow soil at elevations below 1100 m. Flowering from November to May.

Notes —The variation in Chamaecrista mimosoides has led various authors to recognise a number of different forms within the species. Brenan (1967) in his treatment of the Tropical East African species of the genus recognised seven forms. In southern Africa, however, Gordon-Gray (1977) recognised three separate forms. Form 1 was distinguished from typical C. mimosoides by its erect stems, often branching in the upper half ( Fig. 1C ), large, sessile, elliptic extrafloral nectaries that overlap the sides of the petiole, short pedicels and small pale flowers. This taxon is largely confined to the coastal areas of KwaZulu-Natal. Form 2 was distinguished by its low, rounded growth habit ( Fig. 1A ), small, circular-elliptic or circular extrafloral nectaries, and short pedicels bearing small pale yellow flowers. This taxon is widely distributed in KwaZulu-Natal, extending to the Eastern Cape and Mpumalanga Provinces. Form 3, distinguished by the small, subsessile to sessile extrafloral nectaries, and larger bright yellow flowers from other forms is known from Chirundi in Namibia through Katima Mulilo to Tsumkwe, extending to Botswana and beyond the region to Zimbabwe.

After examination of available herbarium material and field studies, the three forms are now recognised as separate species. Form 1, distinguished by its erect stems, branched in the upper half, the large, sessile, elliptic extrafloral nectaries that overlap the sides of petiole, short pedicels, and small pale flowers with 10 stamens and anthers that are divided into two series (6 small, 2–4 mm long; 4 large, 5–10 mm long) is now recognised as the separate species Chamaecrista grandiglandulata (described herein as new). Form 3, distinguished by small, subsessile to sessile extrafloral nectaries, and slightly larger bright flowers with 9–10 stamens divided into three series (2(3) small 2–3 mm long, 4 medium ± 4 mm long, 4 large ± 5 mm long) is now recognised as separate species Chamaecrista gordon-grayei (described herein as new). Gordon-Gray (1977) erroneously considered form 3 as the typical form of Chamaecrista mimosoides , however, this form differs from the type of Chamaecrista mimosoides by the subsessile to sessile extrafloral nectaries, and development of branched and long pedicels. In addition, we recognise two separate forms within C. gordon-grayei distinguished by short pedicels 7–10 mm long, and long pedicels 15–30 mm long. Of these forms, we relegate the form with long pedicels to subspecific level and recognise it as C. gordon-grayei subsp. longipedicellata . No other characters were found warranting the idea of raising the form with long pedicels to species rank.

Form 2, distinguished by small, circular extrafloral nectaries, and short pedicels bearing small pale yellow flowers with 9–10 stamens divided into three series (2(3) small 2–3 mm long, 4 medium ± 4 mm long, (3)4 large ± 5 mm long) resembles the lectotype of Chamaecrista mimosoides designated by Larsen et al. in Aubreville & Leroy (ed.), Fl. Cambodge Loas Viet-Nam 18: 105 (1980). We therefore recognised it as typical C. mimosoides . Future studies should investigate Chamaecrista mimosoides across its wide distribution range to determine whether it is in fact only one widespread taxon.

Additional Specimens Examined — South Africa. — MPUMALANGA: 2530 (Lydenburg): 20 km from Lydenburg on road to Dullstroom (–AC), 05 Mar 1979, Germishuizen 1072 ( NH) . 2531 (Komatipoort): Barberton (–CC), Jul 1915, Thorncroft 885 ( PRE) . — KWAZULU-NATAL: 2730 (Vryheid): Itala Nature Reserve (–DD), 23 Jan 1978, McDonald 495 ( NU) . 2731 (Louwsburg): Jozini dam (–BD), 13 Dec 1965, Burtt 3215 ( NU) . 2732 (Ubombo): Nkuzi Game Reserve, Mougeue (Stand 4) (–CB), 10 May 1976, Goodman 655 ( NU) . 2930 (Pietermaritzburg): Shongweni dam (–CB), 22 Feb 1966, Morris 772 ( NU) ; Isipingo flats (–DD), 20 Mar 1968, Ward 6527 ( NU) . 2931 (Stanger): Beachwood, Durban (–CC), 7 Dec 1956, Lawson 321 ( NU) . — EASTERN CAPE: 3129 (Port St. Johns): banks of Umgazana River (–CB), Apr 1976, Gans 43 ( NU) .

Swaziland ( Eswatini). —2631 (Mbabane): Komati old ferry (–AC), 18 Feb 1960, Compton 29826 ( NH) .

Figures

FIG. 3. Extrafloral nectaries of Chamaecrista species. A. C. mimosoides, sessile, circular or circular-elliptic. B. C. capensis var. capensis, circular, sub-sessile or attached on small stalk. C. C. biensis, circular, concave, sub-sessile or raised on small stalk. D. C. comosa subsp. capriconia, elliptic, sessile, spreading over the petiole. E. C. comosa subsp. comosa, sessile, slightly sunken in petiole. F. C. grandiglandulata, large, sessile, elliptic, overlapping the sides of petiole. G. C. gordon-grayei subsp. longipedicellata, sub-sessile to sessile, circular. H. C. falcata, extrafloral nectaries, long stalked, concave on top. Vouchers: A. Burtt & Hilliard 3215 (NU). B. Walker 119 (PRE). C. Phelan 1120 (PRE). D. Burger 292 (PRE). E. Arnold 792 (NU). F. Ward 1219 (NH). G. De Winter and Wiss 4423 (PRE). H. Ward 2439 (PRE).Scale bars = 5 mm).

FIG. 14. Known distribution of Chamaecrista mimosoides in southern Africa.

FIG. 1. General morphology of Chamaecrista. A. Habit of C. mimosoides showing a low-growing growth form. B. Habit of C. capensis var. flaoescens showing a large flower. C. Habit of C. grandiglandulata branching in the upper half, showing short pedicels and small pale flowers. D. Habit of C. comosa subsp. comosa showing broad leaflets, 2–5 mm wide. E. Habit of C. biensis showing a prostrate or decumbent growth form and small flowers. F. Habit of C. stricta, growth form and small flowers. G. Habit of C. plumosa var. erecta. Photographs A–D, G taken by Liada Musandiwa, E–F taken by Anthony Magee.