Description:

• Evergreen herbs with short to long rhizomes
• Leaves sword-shaped to linear or terete, distichous, crowded basally, usually a few also cauline
• Stem rounded to compressed and 2-sided, or strongly winged, simple or branched, bearing reduced leaves below or leafless except for a subterminal leaflet
• Inflorescences 1-many binate rhipidia (flower-clusters in 2 series, unless reduced to 1 or 2 flowers), either terminal on main and secondary axes or axillary, then stalked or sessile; spathes green or partly to entirely membranous or scarious, margins entire, irregularly torn or fringed; floral bracts (within spathes) membranous or scarious, entire, irregularly torn or fringed
• Flowers actinomorphic, frequently sessile, fugaceous, usually dark blue, occasionally pale blue, white or mauve, occasionally with contrasting markings; each lasting a single day; perianth twisting spirally on fading, unscented; nectar produced in one species from perigonal nectaries
• Tepals basally connate for 0.5-2.0 mm, usually subequal, in a few species outer tepals smaller than inner, lanceolate to ovate, usually spreading horizontally or sometimes ascending
• Stamens erect, free; anthers oblong to linear, extrorse; pollen monosulcate, zonasulculate, 2-zonasulculate, or trisulcate, exine reticulate to areolate
• Ovary ovoid to oblong or cylindric-trigonous, usually included in bracts
• Style filiform, eccentric, dividing apically into 3 short stigmatic lobes, occasionally barely 3-fid, lobes entire or fringed
• Capsules ovoid to oblong- or cylindric-trigonous, or broadly 3-winged, subsessile or stalked; remains of perianth usually persisting on capsules
• Seeds rounded to angular, shortly cylindric, or compressed, or depressed and then oriented radially in locules, bearing a white basal elaiosome in 1 species, 2-many per locule, alveolate to smooth, matte, surface papillate to nearly laevigate, sometimes fringed when flattened
• x = 16

Nomenclature:

• Aristea Aiton
  • Aiton: 67 (1789)
  • Weimarck: 1 (1940)
  • Vincent: 214 (1985)

Distribution & Notes:

• Global: Species ± 52, most diverse in southern Africa, extending to Senegal and Ethiopia in the north, and with 7 species in Madagascar
• Southern Africa:
  • In the summer-rainfall area most frequent in well-watered highlands in grassland, rocky outcrops, or marshes
  • In the winter-rainfall area often montane and in rocky sandstone habitats, often flowering in mass after fires

Additional Notes:

• Pollen grains, capsules and seeds of the genus are unusually variable for the family
• Flowers of most species open early in the morning and fade at midday or early in the afternoon and are pollinated by bees foraging for pollen
• A few southwestern Cape species have flowers that are darkly marked and last an entire day and are pollinated by monkey beetles (Scarabaeidae)
• One species, Aristea spiralis, produces nectar and is thought to be pollinated by long-proboscid flies (Philoliche: Tabanidae) foraging for nectar