Trigonotis
Content
Description
Creeping, decumbent or ascending herbs with simple or branched stems, sometimes forming large mats or cushions.
Leaves either in basal rosettes or cauline, alternate, stalked or not, in creeping species sometimes all in one plane by twisting of the petioles.
Flowers solitary, axillary or extra-axillary, or in elongated, terminal or lateral, scorpioid cymes without leaves or bracts, or with the lowermost flowers in the axils of leaf-like bracts.
Stamens isomerous with corolla, filaments very short, inserted in the tube of corolla, anthers opening introrsely with two longitudinal slits.
Ovary composed of 4 or (7-)8-10 carpels on a cup-shaped receptacle, style short, stigma bilobed.
Distribution
Asia-Temperate, Asia-Tropical: Borneo present; New Guinea present; Philippines (Philippines present), Central Asia present, Japan to Malesia present
About 50 species in Central Asia, China, Japan to Malesia: Borneo, Philippines, and New Guinea.
Notes
Zoelleria Warb. has been regarded as the type of a separate, monotypic tribe Zoel- lerieae by Giirke (1897) for the aberrant number of carpels (7-10), but agrees in all other characters with what Stapf described as a new genus Havilandia. Havilandia was characterized by dorsally rounded, laterally compressed nutlets, while in typical Trigonotis they are dorsally angulate and compressed dorso-ventrally. Along with this difference went the growth habit: creeping with solitary, axillary flowers in Havilandia, apically erect with naked or nearly naked cymes in Trigonotis s.str. With the discovery of Trigonotis abata I.M.Johnston, this correlation did not hold any longer: it combined the growth habit of Havilandia with the shape of the nutlets of Trigonotis. For this reason, Johnston united all three genera in 1940. Trigonotis minuta seems to keep a similar intermediate position according to Van Roy en's description of the nutlets. The present treatment closely follows the two excellent papers of Johnston (1940) and Van Roy en (1975).
Trigonotis was usually regarded as a member of Lithospermeae, but Riedl (1968) made it the type genus of a separate tribe Trigonotideae, in which it is the sole member of subtribe Trigonotidinae. Trigonotideae include all those genera which are nearest to the root of the other tribes within Boraginoideae. Its closest relatives outside Trigonotideae seem to be Trigonocaryum and Myosotis. As in the latter, in some of its species nutlets are pyramidate with the areola shortly stipitate.
In the few species counted polyploidy is prevalent with the diploid numbers 2n = 36 or 48.