Houstonia pusilla Schoepf
Family - Rubiaceae
Stems - To +6cm tall, erect, herbaceous, from a weak taproot, 4-angled, often two per plant, winged. Wings often reddish, with minute dentations (at least near the base).
Leaves - Opposite. Lowest leaves petiolate. Petioles to 5-6mm long, glabrous. Blades ovate to lanceolate, acute, entire, glabrous, with translucent teeth on the margins (use a lens to see), to +7mm long, +4mm broad. Upper leaves nearly sessile, thinner than those near the base of the plant, connected at the base by a scarious stipule. Stipule with a triangular point.
Base of plant.
Inflorescence - Single flowers terminating long axillary peduncles. Peduncles to +2cm long, 4-angled, minutely winged. Wings as those of the stem.
Flowers - Corolla purple, with red near the center, 4-lobed, salverform, 1-1.5cm broad, glabrous. Lobes 6-7mm long, 3-4mm broad, oblong, acute. Corolla tube to 5-6mm long, yellowish-green. Stamens 4, alternating with the corolla lobes, included, adnate to the corolla tube in the basal 1/3. Filaments essentially absent. Anthers yellow, ovoid, 1mm long. Style green, glabrous, 1.1mm long. Stigma thicker than style and giving the pair a clavate appearance. Ovary inferior, surrounded by the calyx tube. Calyx tube green, glabrous, 1-2mm long. Calyx lobes 4, erect, glabrous, acuminate, 2.5-3mm long.
Flowering - March - April.
Habitat - Glades, rocky ledges, outcroppings, dry open places.
Origin - Native to U.S.
Other info. - This little species can be found in the southeastern 1/4 of Missouri. The plant is quite striking for its small size and would be a worthy candidate for cultivation in a rock garden.
Photographs taken in Vale, NC., 3-15-03.