Isodon coetsa (Buch.-Ham. ex D.Don) Kudô

Suddee, S., A. J. Paton, & Parnell, J. (2004). A Taxonomic Revision of Tribe Ocimeae Dumort. (Lamiaceae) in Continental South East Asia I. Introduction, Hyptidinae & Hanceolinae. Kew Bulletin, 59(3), 337-378. doi:10.2307/4110949

Distribution

Himalaya, India, Sri Lanka, China, Burma, Laos, Thailand, Vietnam, Philippines, Malaysia & Indonesia.

Ecology

In open bamboo forest, grasslands, disturbed areas, along paths in evergreen forest; 700 - 2200 m.

Morphology General Habit

Erect or ascending perennial herb or undershrub up to 3 m tall, occasionally creeping

Morphology Leaves

Leaves membranous to chartaceous, ovate or ovate-lanceolate, 35 - 120 x 8 - 60 mm, apex acute or acuminate, base obtuse or shortly cuneate, sometimes decurrent on petiole, margin serrate, occasionally dentate, puberulous, scaberulous or softly pubescent with hairs denser on veins above, puberulous on veins otherwise glabrous, or softly pubescent or tomentose all over beneath, dotted with minute sessile glands on both sides or only beneath, veins prominent both sides or only beneath; petioles 5-30 mm long, pubescent

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens included in anterior corolla lip; anterior pair insertion varying from above the middle of corolla tube to around the base of anterior corolla lip, glabrous or only slightly pubescent at base; posterior pair inserted near the base of corolla tube, villous at base

Morphology Reproductive morphology Flowers Calyx

Calyx campanulate, 2 - 3 mm at anthesis, campanulate or tubular-campanulate, 3 - 5 mm long in fruit, inconspicuously 2-lipped; teeth subequal, ovate-triangular, acute at apex, margin sometimes ciliate; tube declinate, 10-nerved, twice or more as long as teeth, glabrescent or hoary pubescent, with sessile glands outside, not gibbous at anterior base; transverse nerves prominent, especially at calyx throat and teeth

Morphology Reproductive morphology Flowers Corolla

Corolla blue or pale purple, occasionally white, declinate, 5 - 10 mm long; posterior lip subequally 4-lobed, lobes rounded or obtuse at apex, pubescent, with sessile glands on back; anterior lip orbicular or ovate-oblong, 2.5 - 6 mm long, concave, glabrous inside, glabrous or pubescent, with sessile glands outside; tube 2.5 - 4 mm long, tubular, abruptly expanded above the narrow base and slightly gibbous on posterior side, pubescent on anterior side inside, pubescent, with or without sessile glands outside

Morphology Reproductive morphology Flowers Disc

Disc with anterior side slightly developed, lobes obscure

Morphology Reproductive morphology Flowers Gynoecium Style

Style shorter or longer than stamens, included or exceeding anterior corolla lip

Morphology Reproductive morphology Fruits

Nutlets brown or black, ovoid or oblong, c. 1 mm long, smooth or tuberculate, producing mucilage when wet or not.

Morphology Reproductive morphology Inflorescences

Inflorescence terminal and axillary, composed of several lax narrow raceme-like branches, forming a large panicle; cymes lax or dense 3 - 7-flowered, sometimes corymbose appearance; bracts ovate, ovate-lanceolate, lanceolate or orbicular; bracteoles linear or linear-oblong, c. 1 mm long, pubescent, caducous or persistent; pedicels 1 - 3 mm long at anthesis, 3 - 5 mm long in fruit, glabrescent to pubescent

Morphology Stem

Stems sometimes woody at base, much branched, hollow, quadrangular, rounded or round-quadrangular, glabrous, glabrescent or pubescent, sometimes tomentose

Note

After study of the types and other specimens from different parts of Asia, we conclude that this species is extremely variable in hairiness, and in leaf, corolla and calyx size. There is no clear discontinuity in these characters, especially in the indumentum of the stem and leaf which most of the previous works have used to split this species into varieties. Murata (1971) did not recognise varieties and placed the hairy forms P. menthoides, P. macraei, P. rugosus var. tomentosus and P. cavaleriei as synonyms of Isodon coetsa. Li (1988 & in Li & Hedge 1994) recognised the hairy form as Isodon coetsa var. cavaleriei and also mentioned that this species is variable. He placed P. macraei as a synonym of I. coetsa var. cavaleriei but recognised P. menthoides as a synonym under I. coetsa var. coetsa. Li (1988) recognised I. javanicus as a separate species from I. coetsa and placed it in a different series. There is no clear discontinuity in characters to divide this variable species into varieties. Existing keys are difficult to use. To reduce the confusion surrounding the names and to produce a functional taxonomy, the names above are here reduced to synonymy under I. coetsa.

Phenology

Flowering August -January, fruiting October - April.

Type

Nepal, Narainhetty, 21 Oct. 1802, Buch.-Ham. s.n. (holotype BM!). Ocimum coetsa (Buch.-Ham. ex D.