Plant: Shrub to 4 m, usually with paired spines at nodes aging white Leaves: leaves alternate, twice compound with 3-5 pinnae Flowers: flowers yellow, in dense globose heads Fruit: a linear strait-slightly curved pod, strongly constricted between seeds. Note: #1556 large specimen collected 5 miles north of Hunter Wash with minute spines, sometimes referred to as var. paucispinus. References: Kearney & Peebles; Arizona Flora. McDougall; Seed plants of Northern Arizona. ASU specimans