Leaves are numerous, opposite, and borne directly on the stem. They are lance-shaped and tend to be a purplish green. Venation is pinnate. Inflorescences are unbranched flowering stalks. Small green leaflike bracts occur at the base of each flower.
Corollas are purple to magenta often with red spots on the inside.
The upper two limbs are slightly longer and over arch the lower three, creating a weakly bilateral shape. The four stamens four are covered with silky hairs. The upper two stamens are shorter th an the lower tw o. Stamens do not extend beyond the corolla. Each flower has one pistil with a long style. Fruits are capsules that split open along several vertical lines.