Habit: Dwarf perennials with thickened roots. The stems are much reduced and during periods of drought the plants retract into the sandy soil. This has been ascribed to contractile roots, but no such roots are present in either species. However, in Frithia the cells of the leaves are arranged in columnar, axial rows and when moisture is lost and the cells shrink, the tangential walls contract. Artificially induced dessication using silica gel, indicated that a leaf may contract to up to one third of its length. This causes the plants to retract into the soil, a mechanism which renders protection to the plants during times of drought. Retraction into the ground is thus achieved by means of 'contractile leaves, not contractile roots. Roots: Roots of Frithia pulchra differ from those of F. humilis in being more fibrous, possibly because of the drier conditions prevailing in its habitat and the strategy to insulate the plants against the heat of surrounding rocks in summer. Leaves: Borne spirally, the leaves of both species are cylindrical with windowed tips and are covered by an epidermal layer of waxy idioblasts arranged in distinct rows. Leaves 15-25 mm long, blue-green or grey-green. Window of leaf tips convex with no markings along margins.Flowers: Flowers in both species are borne singly and on very short stalks or are stalkless. They are subtended by five unequal sepals closely resembling the cylindrical leaves. The petals are bright magenta with gold, yellow or white centre, 25-35 mm diam.; number between 30 and 45 in F. pulchra and tend to have blunt, rounded tips, whereas those of F. humilis number between 20 and 30 and usually have acuminate tips. Pollen: Pollen in both species of Frithia is yellow. The grains are tricolpate and simplicolumellate in F. pulchra with a perforate surface and lumens of different sizes. Pollen in F. humilis has a perforate surface, and is pluricolumellate, with lumens of more or less equal size. Fruit: Fruits are hygrochastic capsules, the shape resembling a barrel. Thick tissue surrounds the capsules of F. pulchra, whereas that of F. humilis is more fragile. However, this character is not constant for the two species and seems to vary with environmental conditions. Capsules of both species tend to break up shortly after ripening. In both species, there are five or six locules, no valve wings and no closing bodies. Expanding keels are parallel with divergent tips, and are dark brown in F. pulchra and lighter brown in F. humilis. Covering membranes are reduced to a ledge in both cases.Seeds: In F. pulchra the end where the seed has been attached to the funicle (hilar end) has a sharp point, whereas in F. humilis it is more rounded. The surface of the epidermal cells differs markedly between the two species, that of F. pulchra being rough-textured whereas the cell surface of F. humilis is smoother.
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