1. White-stemmed Mentzelia Mentzelia albicaulis - Plants annual with petals less than 1.5 cm long. Floral bracts entire. Flower clusters not leafy.

2. Small-flowered Mentzelia Mentzelia dispersa - Plants annual with petals less than 1.5 cm long. Flowers in leafy clusters. Basal leaves less than 10 cm long with entire to lobed margins. Stem leaves entire to dentate. Floral bracts ovate or tapered from middle to tip with entire to lobed margins. Sepals 1-3.5 mm long. Fruits 7-25 mm long, 1-2.5 mm wide and straight or curved less than 30 degrees.