Cassia L., Sp. Pl.: 376. 1753.

Figs 22, 30, 31

Cathartocarpus Pers., Syn. Pl. 1: 459. 1805. Type: Cathartocarpus fistula (L.) Pers. [≡ Cassia fistula L.]

Bactyrilobium Willd., Enum. Pl.: 439. 1809. Type: Bactyrilobium fistula (L.) Willd. [≡ Cassia fistula L.]

Cassiana Raf., Amer. Monthly Mag. & Crit. Rev. 1: 266. 1818. Type not designated.

Mac-leayia Montrouz., Mém . Acad. Imp. Sci. Lyon, Sect. Sci., sér . 2, 10: 198. 1860. Type: Mac-leayia multiflora Montrouz. [= Cassia artensis Beauvis.]

Type.

Cassia fistula L.

Description.

Trees or shrubs, lacking spines or prickles. Stipules 0.1-1.0 cm, in general caducous. Leaves distichous or spiral, paripinnate; extrafloral nectaries absent; leaflets 2-25 pairs, opposite. Inflorescence an axillary raceme; bract 1, caducous or persistent, bracteoles 2, at the base of pedicels, usually caducous. Flowers hypogynous, bilaterally symmetrical, hypanthium solid, turbinate or conic; sepals 5, free, reflexed at anthesis; petals 5, yellow or pink, less often red, white or mixed, the median petal a different colour from the rest; stamens 10, heteromorphic, 3 with long sigmoidal filaments and longitudinally dehiscent anthers, 7 adaxial ones varying in length, organised in groups of 5+2 or 4+3, anthers with basal poricidal dehiscence; pollen unknown; ovary shortly stipitate, attached to the base of the hypanthium. Fruit a linear-oblong, often long, cylindrical or quadrangular, woody, indehiscent legume (except in C. hintoni Sandwith). Seeds obovoid to ellipsoid, compressed, smooth and glossy with castaneous or brownish testa.

Chromosome number.

Haploid numbers n = 12, 13, 14 (Goldblatt and Johnson 1979 -).

Included species and geographic distribution.

Thirty-nine species (LPWG 2022), pantropical with two main centres of diversity, in the Neotropical region (13 species), mainly in the Amazon and Atlantic Forest, and in sub-Saharan Africa (10 species). Other species occur in South and South East Asia and in Oceania (Fig. 31).

Ecology.

Cassia occurs preferentially in tropical rainforests; a few species extend to or occur exclusively in temperate areas, such as C. ferruginea Schrad. ex DC. and C. leptophylla Vogel (Queiroz 2009; Scheidegger and Rando 2020).

Human uses.

Many uses are reported for several Cassia species as medicinal plants (Lewis 2005a). Cassia fistula, C. grandis L.f., C. javanica L. and C. roxburghii DC. are widely cultivated ornamentals across tropical and subtropical regions owing to the beautiful flowers and dense inflorescences (Scheidegger and Rando 2020).

Etymology.

Derived from the ancient Greek name casia for the aromatic and fragrant plants (Lewis 2005a).

Notes.

Cassia is characterised by showy dense inflorescences, flowers with an androecium with 3 long sigmoidal stamens with longitudinally dehiscent anthers and 7 adaxial stamens varying in length, organised in groups of 5+2 or 4+3, and these poricidal at the base of the thecae (instead of apically as in Chamaecrista and Senna) (Fig. 22). The fruits are also characteristic: indehiscent, woody, and cylindrical or quadrangular. There is no comprehensive phylogeny for the genus: fewer than 10 taxa have been sequenced, and mostly for different loci. Thus, the relationship among species, and the biogeography and morphological evolution, are poorly known.

Taxonomic references.

Irwin and Barneby (1982); Lewis (2005a); Queiroz (2009); Scheidegger and Rando (2020).