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..
Herbs, with serrate, crenate or lobed leaves, and solitary or clustered, axillary or terminal, perfect flowers. Bractlets of the involucels none. Calyx 5-toothed or 5-cleft. Stamen-column anther-bearing at the summit. Cells of the ovary 5-∞, I-ovuled; style-branches of the same number, stigmatic at the summit only. Carpels indehiscent, or at length 2-valved at the apex. Seed pendulous. [Greek, used by Theophrastus.]
About 100 species, natives of the warmer parts of America, Asia, Africa and Australasia. Besides the following, some 20 others occur in the southern and southwestern parts of the United States. Type species: Sida alnifolia L.
Leaves linear, ovate or oblong, serrate
Leaves ovate or oblong-lanceolate; flowers 2"-4" broad
Leaves linear or linear-oblong; flowers 6"-12" broad.
Leaves palmately 3-7-lobed.
Glabrous or nearly so, tall; flowers in terminal panicles.
Densely stellate-canescent, low: flowers axillary.
Sida spinosa L. Sp. Pl. 683. 1753.
Annual, erect, branching, finely and softly pubescent, 1°-2° high. Leaves ovate to oblong-lanceolate, 1'-2' long, 5"-10" wide, petioled, obtuse or acute, truncate or cordate at the base, crenate-dentate; flowers axillary, short-peduncled, yellow, 2"-4" broad; peduncles shorter than the petioles; calyx-teeth triangular, acute; carpels 5, dehiscent at the apex into 2 beaks; stipules linear; petioles of the larger leaves with a small spinelike tubercle at the base.
In waste places, Maine to New Jersey, Iowa and Michigan, Kansas, Florida and Texas, and widely distributed in tropical America. Supposed by some to be naturalized at the north, but it occurs in New Jersey as if native. Summer.
Sida Elliottii T. & G. Fl. N. A. I: 231. 1838.
Perennial, glabrous or nearly so, branching, 1°-4° high. Leaves short-petioled, linear or linear-oblong, 1'-2' long, 2"-2 1/2" wide, mostly obtuse at each end, serrate-dentate; peduncles I-flowered, often longer than the petioles; flowers axillary, yellow, 6"-12" broad, calyx-teeth broadly ovate, acute; carpels 8-10, dehiscent at the apex, slightly and abruptly pointed.
In dry soil, southern Virginia to Florida, west to Missouri and Chihuahua. Summer.