Herbaceous or ± shrubby perennials; stem woody, fibrous, sometimes resinous, simple or dichasially branched, covered with persistent leaves or their imbricate sheaths, or a dwarf caespitose herb (Acanthochlamys). Leaves tristichous or spirotristichously arranged, clustered at end of the stem or its branches when new, the grasslike (rarely subterete) blades linear, rarely acerose, dorsiventral, basally sheathing, entire or often dentate-spinulose along margins, usually reflexing with age, or caducous along a regular, usually straight transverse line. Adventitious roots, if present, alternating with the leaves, penetrating the lower, old, fibrous leaf sheaths in their downward growth. Inflorescences terminal, becoming lateral by elongation of axis, 1-many-flowered, their scapes caducous, or (in Acanthochlamys) a compound capitulum on a scape arising from the rhizome, at the base usually surrounded by 3 leaflike aristate bracts, the peduncle bearing 5-8 few-flowered capitula, the flowers subtended by aristate bractlets. Flowers perfect or rarely unisexual (Barbaceniopsis), actinomorphic, usually brightly coloured, epigynous or rarely hemiepigynous (Vellozia hemisphaerica and allied spp.). Hypanthium equaling or often exceeding the ovary in length and adnate to it, often provided with a corona dorsal to the stamens and usually united to them. Tepals 6, in 2 whorls, generally all similar, blue, lilac, white, yellow, orange, red, pink, purplish or green, erect to reflexed at anthesis. Stamens 6 to numerous, then in 6 bundles; filaments free, terete, simple and often bearing basal appendages ventrally (Vellozia), or adnate to the corona (Barbacenia), or fused with the tepals (Barbaceniopsis, Xerophyta), or borne on the corolla lobes and short (Acanthoclamys); anthers elongated or oblong, 2-thecate, 2- or 4-sporangiate, exceptionally 10-sporangiate (X. schnizleiniana, Menezes 1980), basifixed to dorsifixed, introrse, or rarely extrorse; each theca (rarely each pollen sac) opening by a longitudinal slit. Ovary either three-locular, often depressed at apex or the walls prolonged upwards into a hypanthium, or oravy unilocular in the upper part and 3-locular in lower part (Acanthochlamys); style slender but usually enlarged towards the stigmas; stigmas 3, apical or subapical, distinct to wholly confluent, linear to orbicular, or stigma trilobate (Acanthochlamys); ovules numerous, anatropous, bitegmic; placentas stalked, expanded, 2 in each locule, axile. Septal nectaries present in ovary walls (except in Acanthochlamys). Fruit a capsule, usually loculicidally dehiscent by slits and/or pores; seeds numerous; embryo small; endosperm copious, starchy, non-farinaceous.
Most species prefer specific substrates such as bare granite or quartzite, some occur on sandstone, sand or humus; in Madagascar substrates such as granite, limestone or sandstone are populated. With the exception of Talbotia, which grows in moist shade, the Velloziaceae are adapted to highly xeric conditions. When the dry plants are moistened, water is absorbed immediately from the leaves or leaf sheaths as if they were made of blotting paper, and the plants appear more or less explicitly poikilohydrous. Species growing in extreme aridity (Xerophyta) have been shown to have a drought tolerance of 0% relative humidity, i.e. they revive after losing all the water capable of diffusion at 28 ºC (Gaff 1977). Acanthochlamys occurs in the subalpine aciculignose shrub-meadow region at an altitude of 2700-3500 m.
In the Old World, the family is distributed from Madagascar and S Africa in the south to Angola in the NW and Ethiopia and further with a single species across to SW Arabia in the NE. Acanthochlamys bracteata is restricted to the Hengduan Mountains at the SE margin of the Kang-Zang Plateau of SW China (Xiangcheng, Daocheng, Daofu of W Sichuan to Zhag'yab of Tibet). In the New World, the distribution extends from Brazil and NW Argentina to NE Brazil, Venezuela and Panama and includes also Andean countries; the Amazon Basin is largely excluded. Many species are highly endemic and grow in inaccessible localities. In the Brazilian central mountains the quartzitic Serra do Espinhaço is the centre of diversity of the family.
The majority of this description is the text of Velloziaceae writen by Kubitzki (1998), with statements relating to Acanthoclamys (treated as a family in it's own right by Kao and Kubitzki (1998)). With kind permission from Springer Science+Business Media: This work is subject to copyright. All rights reserved, whether whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, broadcasting reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under German Copyright Law.All Rights Reserved