3. Glossopetalon A. Gray, Smithsonian Contr. Knowl. 5(6): 29, plate 12, fig. B. 1853.
Greasebush [Greek glossa, tongue, and petalon, spreading, alluding to outspreading tongue-like petals]
Shrubs. Stems densely branched, ˂branches ascending or divaricate˃; twigs yellowish green to green or grayish green, eventually turning yellowish brown to orangish brown, with fine decurrent ridges, punctate (sometimes inconspicuously), glabrous or puberulent; bark becoming gray to dark gray, pale yellow, or dark brown, sometimes with black patches. Leaves alternate; stipules absent or usually relatively small (often adnate proximally to petiole and appearing as a pair of minute lobes), triangular to subulate or filiform; petiole usually short, persistent after leaves are shed, base sometimes glandular-thickened, becoming darkened, decurrent as fine ridges proximal to nodes; blade narrowly elliptic to oblanceolate, base angled or tapered, margins entire, apex tip rounded or, more commonly, blunt to sharply pointed, sometimes mucronate (spinescent in G. pungens), ˂midvein sometimes apparent as low keel proximally on abaxial surfaces˃, venation obscure, sometimes inconspicuously punctate, usually glaucous, glabrous or puberulent. Inflorescences terminal or axillary (then terminating short shoots), flowers solitary, sometimes 2–3-flowered clusters. Pedicels mostly short. Flowers: hypanthium lined with fleshy, crenately lobed nectar disc; sepals 3–5(–6), ovate to nearly circular, sometimes slightly concave at base, not cucullate, margins hyaline, glaucous, glabrous; petals ˂persistent at fruiting˃, 3–5(–6), white, ˂spirally twisted with age˃, narrowly elliptic-oblanceolate to oblanceolate, 2–9 mm; stamens 4–10 in 1–2 series, filaments inserted along disc margin, equal to or longer than anthers; carpels 1(–3), distinct, sessile; stigmas oblique, capitate. Follicles 1(–3), asymmetrically ovoid to obovoid or ellipsoid, turgid or slightly angular-flattened, adaxial surface curved or ± contorted prior to dehiscence, ˂apex often appearing ± beaked˃, longitudinally striate with prominent venation, glabrous or, occasionally, sparsely puberulent; adaxial suture ˂narrow˃, ± cartilaginous. Seeds 1 or 2 per follicle, usually tan or yellowish, sometimes brownish white or cream, spheric or somewhat reniform, shiny, smooth or minutely reticulate/pitted; arils white (drying tan), irregularly discoid or ± fimbrillate.
Species 4 (4 in the flora): w, c United States, Mexico.
Glossopetalon is treated here as comprising one relatively widespread and morphologically variable species and three narrowly endemic, more morphologically homogeneous relatives. The plants occur mostly on calcareous substrates. Taxa within Glossopetalon are relatively character-poor, especially on herbarium specimens, and the characters used to distinguish taxa in past treatments are variable among populations. The genus is in need of more detailed study using biosystematic and molecular methods. In navigating the keys, characters of leaf shape, stipule development, and numbers and shapes of perianth parts should be studied closely by observing multiple examples of a given structure from a specimen in order to facilitate determinations. Rapidly expanding extension shoots sometimes produce atypical leaves that are larger and broader than the limits stated in the keys and descriptions.
Forsellesia Greene, often included as a synonym of Glossopetalon, is an illegitimate name.
SELECTED REFERENCES Ensign, M. R. 1942. A revision of the celastraceous genus Forsellesia (Glossopetalon). Amer. Midl. Naturalist 27: 501–511. Holmgren, N. H. 1988. Glossopetalon (Crossosomataceae) and a new variety of G. spinescens from the Great Basin, U.S.A. Brittonia 40: 269–274. Thorne, R. F. and R. Scoggin. 1978. Forsellesia Greene (Glossopetalon Gray), a third genus in the Crossosomataceae, Rosineae, Rosales. Aliso 9: 171–178.