This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Mostly annual branching pubescent herbs, the branches often prostrate, with opposite stipules evenly pinnate leaves, and solitary axillary peduncled yellow flowers. Sepals usually 5, persistent or deciduous. Petals the same number, obovate or oblanceolate, deciduous. Stamens twice as many as the petals. Ovary sessile, 10-12-celled; ovule 1 in each cavity, pendulous; style long, or short, 10-12-grooved, persistent; stigma mostly 10-12-ridged. Fruit 10-12-lobed, not spiny, often tubercled, splitting into 10-12 I-seeded segments. [In honor of Kallstroem.]
About 20 species, of wide distribution in warm and tropical regions. Besides the following, 7 others occur in the southern and western States. Type species: Tribulus maximus L..
Persistent style longer than the carpel-bodies; carpel-faces scarcely wrinkled; petals 3 1/2"-5" long.
Persistent style shorter than the carpel-bodies; carpel-faces prominently wrinkled:
Kallstroemia intermedia Rydb. N. Am. Fl. 25: 113. 1910.
Annual, branches slender, hirsute and pilose, prostrate, 6'-18' long. Leaves short-petioled; stipules subulate, shorter than the petioles; leaflets 3-5 pairs, oval, or oblong, inequilateral, acute or obtuse at the apex, rounded or subcordate at the base, 4"-10" long; peduncles slender, 6"-2' long in fruit; flowers 1' broad, or less; sepals linear-lanceolate, very pubescent, persistent, shorter than the petals; fruit ovoid-conic, strigose-canescent, about 3" in diameter, shorter than the stout persistent style, the segments tubercled.
Kallstroemia hirsutissima Vail, in Small, Fl. SE. U. S. 670. 1903.
Annual, branches stout, appressed cinereous-pubescent and hirsute. Leaves short-petioled; stipules lanceolate; leaflets 3-.: pairs, elliptic, 4"-10" long, shaggy-hirsute,at least beneath; peduncles stoutish, 5"-8" long; flowers 6"-7" broad, yellow or orange-yellow, fading whitish; sepals linear-lanceolate, as long as the petals or nearly so; fruit broadly ovoid-conic, 3"-4" in diameter, longer than the conic style, the segments sharply tubercled.
In dry soil, Kansas and Colorado to Texas, New Mexico and Mexico. July-Aug.