Noel H. Holmgren in Flora of North America (vol. 4)
dioecious or monoecious, spinescent; herbage scurfy-puberulent when young, mostly with branched hairs, becoming glabrate.
erect, much branched, woody throughout, not jointed, forming a rounded bush; younger branches ribbed, rigid; lateral branches becoming spinescent.
alternate, succulent or coriaceous; blade with midveins prominent, spatulate to oblanceolate, sometimes narrowly so, base gradually tapering to petiole, margins entire, apex rounded to obtuse.
terminal, spikelike clusters.
unisexual; staminate in 2-5-flowered clusters in bract axils, perianth 4(-5)-parted, equaling or slightly longer than stamens, stamens 4-5; pistillate in 1
few-flowered clusters per glomerule, each closely invested by 2 wholly united bracts, perianth absent; stigma 2-lobed.
bracts forming flattened, samaralike fruiting structure around utricle, margins thickened, spongy within; pericarp free.
vertical, compressed-lenticular, seed coat brown, tuberculate; embryo annular; perisperm copious.
Species within checklist:
Rainbow Bridge National Monument