This prostrate weedy annual occurs mostly from the Great Plains to Central America. It has been reported from CRIT (EKY, redet. as humistrata) and WARR (Pr), but verified colls. have not been seen. It is widely scattered on fertile bottomlands along larger rivers in Mo. (Y) and is recorded from most other states adjacent to Ky. (K). It is consider native and rare in Ind. and Ohio (NS). C. serpens has been confused with maculata and allied species, but it is completely glabrous, with small (2-7 mm long), oblong to suborbicular, entire, often reddish-margined leaves, and with two fused scalelike stipules, often lobed or fringed (versus two separate lacerate stipules appearing as four per node); 2n = 22 (FNA 12, W, Y). Two related western species may also be expected as adventives in Ky. (W) and have been reported, but apparently in error (M): C. serpyllifolia (Pers.) Small and C. glyptosperma (Engelm.) Small.