Baby Jump-ups (Mecardonia procumbens) only grow in moist areas such as seeps or along streams here in the southwestern US, but Baby Jump-ups are more widespread in the extreme southern US and in tropical regions to the south.
I discovered several of these small, native wildflowers growing along the stream in Sabino Canyon here in Tucson in September.
I have no idea how Baby Jump-ups got their rather silly sounding common name, but their tubular flowers are fairly small, usually less than 1/2 inch (~1.2 cm) long. The flowers have 2 united upper lobes, 3 lower lobes, and a brown-lined throat. The bright yellow flowers are nestled in 3 leafy green bracts.
The leaves are opposite with toothed edges, and they will turn black when dry. This plant has four-angled stems like those in the Mint Family (Lamiaceae), but it is actually in the Figwort Family (Scrophulariaceae) along with snapdragons and penstemons.
There is some confusion with the scientific name of this plant, and it has been incorrectly labeled as Bacopa procumbens in the past.