Danais is characterized by its climbing habit; opposite or sometimes verticillate leaves; interpetiolar, triangular to 2-lobed or fimbriate, generally persistent stipules; terminal and/or axillary, bracteate, cymose inflorescences; bisexual, distylous, generally rather small flowers with basically 5 but generally 4-6 calyx lobes, corolla lobes, and stamens; funnelform to salverform corollas with the lobes valvate-reduplicate in bud and the tubes sometimes fenestrate; 2-lobed stigmas; ovary with 2 locules and numerous ovules in each locule; capsular, loculicidal, subglobose, generally papery to somewhat woody fruits; flattened winged seeds; and often a characteristic yellow-green drying color. The plants often have a foetid odor. The corollas often have remarkably slender tubes, and may be variously white, yellow, orange, red, violet, blue, purple, or nearly black.
Danais is very similar to Payera and Schismatoclada. Buchner & Puff (1993) distinguished Danais from these by its climbing habit, inflorescences that may sometimes be axillary, and loculicidal capsules that are not beaked at the apex; vs. erect trees and shrubs with terminal inflorescences and fruits that are beaked and variously loculicidal or septicidal in Payera and Schismatoclada. However the fruits of some species of Danais are actually shortly beaked (i.e., with the top portion inside the calyx limb prolonged above the calyx limb, so the capsule is slightly semi-inferior), but the capsules of Danais split straight down from the top to below the middle, with the beak portion not splitting further and the seeds released from the inside of the main part of the capsule. In these other two genera, the capsules are semi-inferior and generally split from the top through the beak to near or below the middle of the capsule body, then the pyramidal or tubular beak portion splits again and the seeds are released often mainly through that beak portion.
Buchner & Puff (1993) detailed the morphology and anatomy of the genus, and Puff & Buchner (1994) presented a revision of this genus. The taxonomy here follows Puff & Buchner. Danais fragrans is the most commonly collected species in Madagascar. Several of their species circumscriptions depend strongly on stipule shape; if this varies more than they documented, then some species may need re-evaluation. Flower size and inflorescence position vary widely among Madagscar's Danais species. Buchner & Puff (1993) discussed the diversification in pollination within the genus, which has species variously adaptated for pollination by hawkmoths, by other kinds of moths, and by various diurnal insects. They noted that the flowers of some species are sweetly fragrant, and others appear to have no odor. Puff & Buchner (1994) presented a graphical overview of the species by corolla and fruit sizes, and distribution maps for individual species. The corollas often have colorful lobes (red, orange, yellow, purple) but greenish white or dull white or cream tubes.
For more taxonomic information see TROPICOS. For more information on individual species and synonymy, see the Madagascar Project. (To access that data, in the upper right of this web screen, click on "Choose Project", and then the corresponding database from that list.)