Explanation of each subgenus

Subgenus Ipomoea

This subgenus is divided into two sections, Ipomoea and Pharbitis. This subgenus is considered to be comparatively primitive. The section Pharbitis in particular has the most primitive characteristics and most species have three carpellate pistils (three-lobed gynoecia). Affinity between Polemoniaceae is pointed out.

This subgenus consists of Ipomoea pes-tigridis (Kikuzaasagao),I. nil (Asagao), I. hederacea (Amerikaasagao), I. purpurea (Marubaasagao), and I. indica (Noasagao).

Subgenus Quamoclit

This subgenus includes six sections: Mina (Quamoclit sensu Austin), Calonyction, Batatas and others. This subgenus includes section Batatas, which is comparatively unspecialized, and section Mina (sect. Quamoclit sensu Austin), the most specialized section in genus Ipomoea. The common characteristics of this subgenus are the form and pubescence of the seed.

Subgenus Eriospermum (Hallier f.) Verdc. ex Austin

This subgenus is divided into two sections. This subgenus is the most complicated taxonomic group in genus I. indica. The plants in this subgenus have common characteristics in the form and pubescence of their seeds and in the attachment of the cotyledons in the seedlings.