PLANT: Trees or shrubs, in ours with semi-succulent trunks and branches, the outer bark yellowish to beige, the inner bark bluish-green. LEAVES: alternate, simple, once-pinnate (in ours), or bi-pinnate, mostly odd-pinnate, usually crowded at the end of small branches, exstipulate, glabrous (in ours), the rachis narrowly winged; leaflets (1)3-11(-many), opposite or sub-opposite. INFLORESCENCE: uniflorous or a cyme of 2-5(-6) flowers (in ours) to paniculate, generally appearing before or with the first leaves, mostly bracteate. FLOWERS: small; sepals in ours light green to slightly reddish, triangular, as many as petals, 1-2 mm long (in ours), basally connate, valvate; petals in ours reflexed at anthesis, white-cream colored (in ours) to pale yellow, greenish or reddish, lanceolate, valvate, 3-4 mm long (in ours), 3 (-5) in pistillate flowers, (3-)5 in staminate flowers; stamens in ours about twice the number of petals, in two whorls, inserted in the base of the nectar-disc, mostly smaller and sterile in pistillate flowers, the filaments ca. 1 mm long, the anthers 1.5-2 mm long; nectar-disc annular, 6-10 lobed, light yellowish-cream (in ours); pistil with 2 or in ours 3 carpels with stigma lobes and locules equalling carpels in number, the style short; ovules 2 per locule. FRUIT: with 1 valve per carpel, in ours purplish-green, 5-7 mm long, 5-6 mm wide; peduncle recurved. SEEDS: at maturity with a thin orangish-red aril (in ours), 5-6 mm long. 2n = 22, 24. NOTES: ca. 100 spp. AZ, CA, FL and most of tropical America with the greatest diversity in the tropical deciduous forests of western Mex. (for J. Burser). REFERENCES: Salywon, Andrew. 1999. Burseraceae. Ariz.-Nev. Acad. Sci. 32(1).