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FNA | Family List | FNA Vol. 4 | Cactaceae | Thelocactus

1. Thelocactus bicolor (Galeotti ex Pfeiffer) Britton & Rose, Bull. Torrey Bot. Club. 49: 251. 1922.

Glory-of-Texas, Texas pride

Echinocactus bicolor Galeotti ex Pfeiffer in L. K. G. Pfeiffer and C. F. Otto, Abbild. Beschr. Cact. 2: plate 25. 1848

Stems 3-38 × (2-)4-10(-18) cm; ribs 8-13 (plant often reaching sexual maturity while still entirely tuberculate); areoles spaced 6-20 mm apart along ribs. Spines (8-)12-30 per areole; radial spines (8-)12-20(-27) per areole, straw colored or white, contrasting with all other spines, 9-35(-45) × 0.3-1 mm, adaxial 1-3+ spines of areole strongly flattened, bladelike or ribbonlike, to 4 times wider than thick, 16-75(-100) mm (usually absent from sexually immature plants); central spines (9-)13-42(-58) × (0.2-)0.4-1.5 mm. Flowers: inner tepals rose-pink to magenta, marked with scarlet or orange proximally, sometimes with white band or margins near bases; stigma lobes reddish to red-orange or pale reddish brown or yellowish. Seeds finely papillate with strongly convex testa cells. 2n = 22.

Varieties ca. 4 (2 in the flora): Texas, Mexico.

Thelocactus bicolor varies geographically, and an indefinite number of segregate taxa may deserve recognition in Mexico.

1 Areoles and spines larger; spines red and white, (older spines weather to ashy white), yellow color-form absent; widespread in s Texas and Big Bend region   1a var. bicolor
+ Areoles and spines smaller; spines usually yellow (rarely red, 0-5% in all populations); only in Marathon Basin of n Brewster County, Texas   1b var. flavidispinus


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