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As per efi thread :
The two genera can be differentiated as under
1. Fruit valves costate, acuminate, plant with garlic odor when bruised or broken; inflorescence racemose on small lateral branchlets calyx-limb flaring, corolla lavender . . . . . . . . Mansoa
1. Fruit valves not notably costate, odor when broken not alliaceous. Inflorescence a twice or more trichotomous cymose panicle, leaflet bases rounded or broadly cuneate, pseudostipules inconspicuous or early caducous, tendril often present and conspicuous; calyx-limb not notably flaring; corolla limb whitish to pink or lavender. . . . . . . . . . . . . . ……………………………………………….. . . . . . . Cydista
The presence of garlic smell in Mansoa and its absence in Cydista is crucial difference in practice.

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Pl. go through Mansoa page (‎‎‎‎Bignoniaceae) with images of species in efloraofindia (done by …).

If you find any mis-identification, pl. let us know.
If anybody can send images of other species of this genera (for incorporation in the website), it will be really nice. Also, if anybody is interested to take up the activity of inserting images on efloraofindia pages from efloraofindia posts, pl. let us know.