Author: Linnaeus
Morphological description
Deciduous or semideciduous tree , 10-15 m tall, rarely more (fistula Cassia tree 386531); young twigs glabrous, branches spreading. Stipules deltoid, acute, 1-2 mm long, tardily caducous, subglabrous
Leaves paripinnate, with 3-7 pairs of leaflets (fistula Cassia compl FT26 ); petiole terete, 5-8 cm long, glabrous; rachis 10-30 cm long, terete; extrafloral nectaries absent; petiolules 4-6 mm. Leaflets subcoriaceous, ovate-oblong, acute, 7-12 by 4-8 cm, glabrous when mature, shining above; base broadly cuneate.
Inflorescence: (fistula Cassia compl FM21 ) Racemes axillary, 1-few together, pendant, lax, many-flowered, 20-40(-60) cm long; peduncle 2-10 cm; bracts 8-10 mm, ovate, acute, puberulous, early caducous; bracteoles 5-7 mm, linear, puberulous.
Flowers pentamerous, on slender, glabrous pedicels , 3-3.5 cm long (fistula Cassia fl 255219 ). Sepals ovate-elliptic, velutinous outside, 7-10 mm long. Petals golden-yellow, broadly ovate, subequal, 30-35 by 10-15 cm, shortly clawed. Stamens 10: 3 long with sigmoidally curved filaments 3-4 cm, anthers 5 mm long, opening by apical and basal slits; 4 shorter with filaments 6-10 mm; anthers opening by a basal pore; reduced stamens 3 with filaments 3-4 mm and minute anthers. Ovary stipitate, strigulose, style velutinous; stigma small.
Pods pendulous, terete, glabrous, black, indehiscent, 20-60 cm long, 1.5-2 cm in diameter (fistula Cassia pods 386530).
Seeds numerous, separated by chartaceous septa and embedded in a glutinous, black pulp, glossy brown, smooth, elliptic, flattened, 8-9 by 5-6 mm (fistula Cassia seeds 256054 ).
Distribution
Probably native of India and Ceylon and perhaps in Burma and N Thailand, now widespread in the tropics, also in the New World. De Wit (1956: 207) discusses in detail whether it is native in the Malesian area and compares the distribution with that of the other monsoon species as, e.g., Bauhinia viridescens , Bauhinia malabarica , Bauhinia pottsii , Cassia javanica and Tectona grandis (Lab.), all bicentric in their distribution, avoiding the humid tropics; this points towards a relict distribution pattern. It is thus possible that C. fistula is indigenous to the monsoon part of Indonesia. It is most certainly introduced to the Malay Peninsula and the Philippines. It has since long time been introduced to China.
Habitat & Ecology
In dry deciduous forests at lower altitudes, in teak forests on Java; it seems to favour calcareous soils and red, volcanic soil; it is also found on sandy and loamy soil in Thailand.
Uses
Besides the ornamental value and the long-time use, also in western medicine, of the pulp in the ripe pods as a laxative, several other parts of the plants have been and still are in use, thus the bark for tanning and as an ingredient in betel paste. A decoction of the roots has been used for purifying wounds. The pods are still imported to health stores in the West. See Heyne (1950: 741), and Burkill (1935: 475).
Note
Cassia fistula forms hybrids with Cassia javanica (see also under this species).