This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - Yellow, 1/2 to 3/4 in. across, terminal and from the leaf axils. Calyx of 4 sepals in 2 pairs; 4 narrow, oblong petals; stamens numerous; 2 styles. Stem: Much branched and spreading from base, 5 to 10 in. high, leafy. Leaves: Opposite, oblong, small, seated on stem.
Preferred Habitat - Dry, sandy soil; pine barrens.
Flowering Season - July - August.
Distribution - Nantucket Island (Mass.), westward to Illinois, south to Florida and Texas.
Because the four pale yellow petals of this flower approach each other in pairs, suggesting a cross with equals arms, the plant was given its name by Linnaeus in 1753. St. Peter's-wort (A. starts), a similar plant, found in the same localities, in bloom at the same time, has larger flowers in small clusters at the tips only of its upright branches.