Key Characteristics: Erect annual herb, a root parasite, 3?15 dm tall, the entire plant yellow (chlorotic),; flowers 5?8 in ± compact, head-like clusters; outer bract lobed in distal 1/2, middle lobe ± lanceolate, tip tapered, inner bract 14?20 mm; corolla 15?20 mm, yellowish, lower side marked maroon in U-shape, pouches white (Wetherwax and Tank 2013). C. rigidus is a variable species with geographically separated but intergrading races (Chuang and Heckard 1986). In our region, it is distinguished rom sspp. rigidus and setigerus by shape of outer inflorescence bracts (see drawings) and generally by color (reddish and with higher chlorophyll concentrations in the latter two subspecies, this perhaps indicating a lesser nutritional reliance on parasitism. (contributed by Cynthia Powell)
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