Tribulus Tourn. ex L.

Herbs, annual to perennial, prostrate to semi-erect, branching, hairy to glabrescent. Leaves opposite, one of each pair alternately smaller or sometimes abortive, paripinnate, stipulate; leaflets 6 - 20, opposite, subsessile to sessile. Flowers solitary, axillary, pedicel-late, usually yellow. Sepals 5, pubescent, deciduous or persistent, imbricate. Petals 5, obovate to obovate-oblong, membranous. Disk annular, 10-lobed. Stamens 5 - 10, outer whorl of 5 slightly longer, opposite the petals; filaments filiform; anthers oblong to ovoid. Each of inner whorl of 5 stamens subtended adaxially by intrastaminal gland and abaxially by extrastaminal gland. Ovary globose,covered with bulbous-based stiff hairs, 5-locular; ovules 1 - 5 in each cell; style simple, cylindrical, 5-ridged; stigma 5-rayed. Schizocarps separating into 4 - 5, dorsally spiny, winged or tubercled., indehiscent, mericarps; seeds obliquely pendulous; endosperm absent; cotyledons ovoid.

Distrib. About 30 species, mainly in tropical and subtropical countries of the World. Five species in India.

Chromosome no. n = 6 (Mallick in Chromo Inf. Servo 7: 7.1966)

KEY TO THE SPECIES

1a. Fruits with spiny mericarps

2

b. Fruits with winged mericarps

2. Tribulus pentandrus

2a. Intrastaminal glands not ciliate, styles glabrous

3

b. Intrastaminal glands ciliate; style pubescent

4. Tribulus subramanyamii

3a. Each mericarp with 4 spines, basal pair of spines sometimes reduced to tubercles

4

b. Each mericarp with 2 median and 20 - 30 dorsal spines, basal pair of spines absent

3. Tribulus rajasthanensis

4a. Pedicels equal to or longer than subtending leaves; style longer than ovary

1. Tribulus lanuginosus

b. Pedicels shorter than subtending leaves; style shorter than ovary

5. Tribulus terrestris

List of Lower Taxa