BURSERACE^ 591 



deciduous bracts; petals fleshy, oval, ofteu acute, pale yellow, and four or five times 

 longer than the glaucous calyx. Fruit nearly fully grown by the end of April and 

 then bright scarlet, about V long, ovate, sometimes falcate, and slightly angled on 

 the ventral suture, becoming dark purple when fully ripe; seeds papillose, orange- 

 brown, about f ' long. 



A round-headed tree, growing occasionally in Florida to the height of 50, with a 

 straight trunk 18'-20' in diameter, slender spreading branches, and stout branchlets 

 pale green and glabrous when they first appear, becoming light brown before the end 

 of the summer, rugose and conspicuously marked during their second season by the 

 large oval leaf-scars. Bark of the trunk ^'-f thick, light red-brown and broken on 

 the surface into broad thick appressed scales. Wood light, soft, close-grained, light 

 brown, with thick rather darker colored sapwood. 



Distribution. Southern Florida from Cape Canaveral to the southern keys and 

 the shores of Bay Biscayne; also in Cuba, Jamaica, Nicaragua, and Brazil. 



XXVI. BURSERACEiE. 



Trees or shrubs, with resinous bark and wood. Leaves alternate, pinnate, 

 without stipules. Flowers perfect or polygamous, in clustered racemes or 

 panicles ; calyx 4-5 lobed, the lobes imbricated in the bud, persistent ; petals 

 45, imbricated in the bud, distinct or slightly united, deciduous ; stamens 

 twice as many as the petals, inserted under the annular or cup-shaped disk ; 

 filaments distinct, subulate ; anthers introrse, 2-celled, the cells opening longi- 

 tudinally ; pistil of 2-5 united carpels ; ov^ary 2-5-celled ; styles united ; 

 stigma 2-5-lobed ; ovules 2 in each cell, pendulous, collateral, anatropous, mi- 

 cropyle superior ; raphe ventral. Fruit drupaceous. Seeds without albumen ; 

 seed-coat membranaceous ; embryo straight ; cotyledons f oliaceous ; radicle 

 short, superior. 



Of the sixteen genera of this family, which is widely distributed through the 

 tropics of the two hemispheres, one only, Bursera, occurs in the United States, 

 reaching the shores of southern Florida with a single arborescent species, and 

 southern Arizona with one shrubby species. 



1. BURSERA, Jacq. 



Trees, with balsamic resinous juices. Leaves alternate, unequally pinnate; leaflets 

 opposite, petiolulate, entire or subserrate, membranaceous. Flowers polygamous, 

 small, on fascicled or rarely solitary pedicels, in short or elongated lateral simple or 

 branched panicles; calyx minute, membranaceous, petals ovate-oblong^ inserted on 

 the base of an annular crenate disk, reflexed at maturity above the middle; stamens 

 inserted on the base of the disk; anthers oblong, attached on the back above the 

 base, usually effete in the pistillate flower; ovary sessile, ovoid, 3-celled, rudimen- 

 tary in the staminate flower; style short; stigma capitate, obtuse, 3-lobed; ovules, 

 suspended below the apex from the central angle. Fruit with a valvate epicarp, 

 globose or oblong-oblique, indistinctly 3-angled; flesh coriaceo-carnose, 2-3-valved; 

 nutlets 1-3, usually solitary, adnate to a persistent fleshy axis, 1-celled, 1-seeded, 

 covered with a thin membranaceous coat. Seed ovoid, without albumen ; seed-coat 

 membranaceous; hilum ventral, below the apex; embryo straight; cotyledons con- 

 tortuplicate. 



Bursera with about forty species is confined to Mexico, Central and South America, 

 and the West Indies. 



