16028 P. argentatum Large stand of grayule with a few plants of marials there and there, gentle slope, south hillside, well-drained lime-stone rubble. Grayule showing some variation but little introgression. Besides individual plants, I selected mass collections were made. One: Plants later flowering, longer, more crooked peduncles, larger plumbos and broader leaves. Two: Peduncles erect, shorter, earlier flowering, smaller plumbos with narrower leaves. 10 mi. Northwest of Ocampo on road to Sierra Mojada, Coah. Aug. 26, 1976 Very accessible locality. Excellent stand.