Wikipedia
Melanthera
Melanthera, squarestem, is a genus of flowering plants in the daisy family, Asteraceae, native to North and South America, as well as Africa, Asia and Oceania, including Hawaii.
The generic name means "black anther."
The most common species of this genus is Melanthera biflora, found in the coastal areas and islands of the tropical belt of the Indo-Pacific region. Together with Portulaca oleracea, Ipomoea pes-caprae and Digitaria ciliaris, Melanthera biflora is usually one of the first species colonizing degraded or altered environments in tropical zones of the planet.
Despite their general hardiness, leaves of Melanthera species are often attacked by rusts such as Uromyces columbianus and Uromyces martinii.