Herbs, terrestrial or among or on rocks, caulescent or without evident stems, occasionally stoloniferous. Leaves rosulate, straight to falcate; blade narrowly triangular, margins spinose. Inflorescences lateral [terminal or lateral], many-flowered, simple or compound and paniculate; branches capitate to lax and elongate; floral bracts broad [broad to narrow], conspicuous. Flowers dimorphic, functionally unisexual, staminate and pistillate on different plants; sepals distinct, symmetric; staminate petals distinct or appearing briefly connate basally from adnation of filaments to adjacent petals; stamens included or exserted; filaments adnate [free or adnate] to petals; pistillate petals distinct, triangular or ovate; ovary largely superior to largely inferior. Capsules ovoid, dehiscent. Seeds narrowly winged to almost wingless, plumose appendages absent. The Texas species are unusual in their scaly capsules and flowers with scaly sepals, petals, and ovaries.