1a.

Flowers bracteates, weakly scorpoid form, with spindle hairs

5. H. longiflorum

1b.

Flowers bracteates, rarely scorpioid cymose, with elliptical pollen grains

H. strigosum

1c.

Flowers unbracteate

2

2a.

Calyx lobes confined, heavy hairs, 4 - 5 mm

H. pterocarpum

2b.

Calyx lobes free, have little hairs or not hairy

3

3a.

Plants annual, nutlets glabrous

5

3b.

Plants perennial, nutlets hairy

4

4a.

Nutlets not winged; stigma abruptly narrowed, filiform

H. lasiocarpum

4b.

Nutlets shortly winged; stigma conical

H. jizanense

5a.

Corolla green; inflorescence up to 15 - 20 cm long

1

5b.

Corolla yellow or white, inflorescence less than 12 cm long

6

6a.

Stigma sessile; flowers white, wood vessels clustered in two groups

H. arbainense

6b.

Stigma narrowly elongate; flowers yellow, wood vessels clustered in three groups

H. zeylanicum