This annual grows up to 1-2 feet tall, either branched or unbranched. It is armed with dense prickles on stems, leaves and fruits (A). The bright yellow flowers are 1 inch or somewhat larger in diameter, and also prickly on the undersides (B,C).  A closer look reveals 5 fused petals with 5 stamens and a single curved style.  The upper 4 stamens are yellow, somewhat resembling a small banana, but the lower one is larger with a curved reddish tip (C,D). The large leaves are deeply cut with wavy margins (B). The fruit is enclosed in a very prickly calyx (A).