M. Thulin (2005) Crossandra. Flora of Somalia 3: 384-388
Plants herbs, subshrubs, or shrubs. Leaves opposite or seemingly in whorls of 4, usually narrowed from below the middle into a long attenuate base. Inflorescences dense terminal or axillary spikes; bracts is 4 rows, persistent, margins entire, toothed, spinulose, or setose, tips often pungent, lower bracts sterile, smaller than the fertile bracts; bracteoles 2, narrow. Calyces deeply 5-lobed, lobes unequal, the upper 2-toothed, broader than the others and often enveloping them; corollas white, yellow, orange, or red, limbs and top of tubes split on the back, forming single 5-lobed lower lips;stamens 4, included; anthers 1-celled, finely bearded; ovaries 2-celled with 2-ovules per cell; styles with obliquely trumpet-shaped stigmas. Capsules ellipsoid, 4-seeded; seeds flattened, covered with fringed scales, sticky when wet.
Crossandra includes about 50 species. They are native in tropical Africa, Madagascar, the southwestern portion of the Arabian Peninsula, and in southeastern Asia.
Global distribution of Crossandra based on records in the global Biodiversity Information Facility. The map suggests that the genus has become well established in the Americas.