Encyclopedia : Taxonomy

Plants and classification of genus Ipomoea

Section Pharbitis

Copyright 1998-2017 Yoshiaki Yoneda

The plants in section Pharbitis have the most primitive characteristics in subgenus Ipomoea, and most species have three carpellar pistils (three-lobed gynoecia).

In the history of taxonomy, Choisy proposed the genus Pharbitis to be independent of and separate from genus Ipomoea, since the sections of Pharbitis have three carpellar pistils. Later, Clark proposed Ipomoea subgenus Pharbitis. After the introduction of botany as a Western science to Japan, the academic name of Pharbitis nil Choisy has been broadly applied to Asagao in Japan. In the field of horticulture, this academic name becam commonly used, and the author also adopted this name until a recent date. However, in the plant classification, Choisy's system is not supported by most taxonomists. The closely related Marubaasagao has been called Ipomoea purpurea (L.) Roth for a long time, and the academic name of Asagao is Ipomoea nil (L.) Roth from the taxonimical point of view". From both historic and gardening points of view, Asagao, the morning glory, is described as Ipomoea nil (Pharbitis nil) in this morning glory database.

Austin and Huaman (1996) investigated plants of Convolvulaceae on the American continents and classified plants of the Ipomoea genus into several subgenera, sections and series. The following shows section Pharbitis in subgenus Ipomoea L.

Subgenus Ipomoea L.

__Section Pharbitis (Choisy) Griseb.

______Series Pharbitis (Choisy) D.F. Austin
__________Marubaasagao Ipomoea purpurea (L.) Roth is included in this series.

______Series Heterophyllae (House) D.F.Austin
__________Amerikaasagao Ipomoea hederacea Jacq.,
__________Noasagao Ipomoea indica (Burm.f) Merr., and
__________Asagao Ipomoea nil (L.) Roth are also included in this series.

______Series Tyrianthinae (House) D.F. Austin

__Section Pharbitis
______section Pharbitis (Choisy) Griseb., Fl.Brit. West Indian Isl.(1864) p.473
__________genus Pharbitis Choisy in Mém. Soc. Phys. Genève (1833) p.438
__________Ipomoea subgenus Pharbitis (Choisy) Clarke in Hook., Fl.Brit. Ind. (1883) p.199

Academic names and synonyms of representative plants in section Pharbitis are as follows. Please refer to the image and the explanation for details of their morphology.

Asagao Ipomoea nil (L.) Roth, of ancient introduction to Japan
__Ipomoea nil (L.) Roth, Cat. Bot. (1797) p.36
______Synonym Convolvulus nil L., Spec. Pl., ed. 2 (1762) p.219 (in part)
__________Pharbitis nil Choisy in Mém. Soc. Phys. Genève (1833) p.439;
__________in DC. Prodr. 9 (1845) p.342

Amerikaasagao Ipomoea hederacea (L.) Jacq., naturalized in Japan
__Ipomoea hederacea (L.) Jacq. Collect.1 (1786) p.124
______Synonym Convolvulus hederaceus L. Sp.Pl.(1753) p.154
__________Pharbitis hederacea Choisy in Mém. Soc. Phys. Genève (1833) p.440;
__________in DC.Prodr.9(1845) p.344

Marubaasagao Common morning glory Ipomoea purpurea (L.) Roth, bred in Europe and North America
__Ipomoea purpurea (L.) Roth, Bot.Abh.(1787) p.27
______Synonym Convolvulus purpureus L., Spec.Pl., ed.2 (1762) p.219
__________Ipomoea hispida Zucc., Cent. Obs. (1806) n.36
__________Pharbitis hispida (Zucc.) Choisy in Mém. Soc. Phys. Genève (1833) p.438
__________Pharbitis purpurea (L.) Voigt, Hort. Suburb. Calc. (1845) p.354

Noasagao Ipomoea indica (Burm.) Merrill, native to Japan
__Ipomoea indica (Burm.) Merrill, Interpr. Rumph. Herb. Amb. (1917) p.445
______Synonym Convolvulus indica Burm., Index Univers. Herb. Amb. (1755) p.6
__________Ipomoea congesta R.Br., Prodr. Fl. Nov. Holl. ed.1 (1810) p.485
__________Convolvulus acuminatus Vahl, Symb.Bot. (1794) p.26
__________Ipomoea acuminata (Vahl) Roem. & Schult., Syst. (1819) p.228
__________Convolvulus congesta (R.Br.) Spreng., Syst. (1825) p.601
__________Pharbitis insularis Choisy in Mém. Soc. Phys. Genève (1833) p.439
__________Pharbitis acuminata (Vahl) Choisy in DC., Prodr. (1845) p.342
__________Pharbitis congesta (R.Br.) Hara, Enum. Sperm. Jap.1 (1948) p.166

  1. Austin, D. F. (1979) An infrageneric classification for Ipomoea(Convolvulaceae) Taxon 28: 359-361.
  2. Austin, D. F. (1986) Nomenclature of the Ipomoea nil complex (Convolvulaceae) Taxon 35: 355-358.
  3. Hatusima, S. (1971) Flora of the Ryukyus p.505 Okinawa Seibutsukyouiku Kenkyuukai.
  4. Hara, H. (1948) Enumeratio Spermatophytarum Japonicarum Pars Prima p.167, Iwanami Shoten.
  5. House, H. D. (1908) The north American species of the genus Ipomoea. Ann. N. Y. Acad. Sci. 18: 181-263.
  6. Iinuma, Y. Makino T. (rev. suppl.) (1907) Zoutei Soumoku Zusetu. Herb part. Volume 4 p.23.
  7. Miyazawa, B. (1960) Illustrated decorative plants p.578 Youkendou.
  8. Ooststroom, S. J. V. (1940) The Convolvulaceae of Malaysia. 3. The genus Ipomoea. Blumea 3: 481-582.

Edited by Yuuji Tsukii (Lab. Biology, Science Research Center, Hosei University)