horizon: a specific layer or stratum of soil or subsoil in a vertical cross section of land
stratum: one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism or a layer of sedimentary rock)
poker alumroot: plant with leathery heart-shaped leaf blades clustered at base of long stalks with greenish-white flowers clustered along the upper part; western North America