ZYGOPHYLLACEAE 669 



15. Xanthoxalis hirsuticaulis Small. Stems loosely tufted on horizontal root- 

 stocks, often stout, 1-2 dm. tall more or less copiously villous-hirsute : leaflets light 

 green, the blades 8-17 mm. wide, usually sparingly strigillose, especially beneath, ciliate : 

 cymes umbel-like, slightly raised above the leaves by the elongating peduncle : pedicels 

 loosely pubescent : sepals oblong or nearly so, -7 mm. long, ciliate all around : petals 

 about 15 mm. long, golden yellow, glabrous : longer filaments glabrous : capsules stout, 

 10-12 mm. long, on more or less reflexed pedicels. [Oxalis hirsuticaulis Small.] 



In rocky or sandy woods, Tennessee and Georgia. Spring and summer. 



16. Xanthoxalis Priceae Small. Stems erect or decumbent from horizontal root- 

 stocks, 1-2 dm. tall, firm, loosely but sparingly pubescent : leaflets deep green, the blades 

 8-13 mm. wide, glabrous, except the sometimes ciliate margins : cymes umbel-like, 

 scarcely surpassing the leaves : pedicels villous : sepals oblong or linear-oblong, about 7 

 mm. long, sparingly ciliate all around : petals about 15 mm. long, golden yellow, pubes- 

 cent without : longer filaments ciliate above ; capsules columnar, stout, 14-17 mm. long, 

 on more or less reflexed pedicels. [Oxalis Priceae Small.] 



In woods and fields, Kentucky to Alabama. Summer and fall. 



FAMILY 5. ZYGOPHYLLACEAE Lindl. CALTROP FAMILY. 



Trees, shrubs, or perennial caulescent herbs, some with an extremely hard and 

 heavy wood, others strong-scented and yielding a bitter and acid gum-resin. 

 Leaves opposite, or alternate by the suppression of one leaf of each pair, the 

 stipules sometimes spine-like : blades abruptly pinnate : leaflets with entire 

 often inequilateral blades. Flowers perfect, regular or nearly so. Calyx of 5, 

 or rarely 46, mostly imbricated or rarely valvate sepals. Disk obsolete or more 

 or less elevated. Corolla of 5 or rarely 4-6, imbricated, valvate or convolute, 

 hypogynous petals, rarely wanting. Androecium of twice as many stamens as 

 there are petals, in 2 series. Filaments distinct, those opposite the petals 

 exterior, larger than the inner and sometimes adnate to the petals. Anthers 

 introrse Gynoecium of usually 2-5 united carpels. Ovary 2-5-celled or rarely 

 10-12-celled, sometimes winged. Styles united. Ovules 2-many, or rarely soli- 

 tary, pendulous or ascending. Fruit capsular, but sometimes baccate at matu- 

 rity, angled or winged, separating into 2-5, or rarely 10 carpels. Seeds 1 or 

 more in each' cavity, with a membranous or fleshy testa. Endosperm wanting 

 or hard. Embryo green, straight or nearly so, with large fleshy cotyledons. 



Herbs : seeds with little or no endosperm. 



Ovary 5-celled, each cavity with transverse septa: fruit armed : seeds several. 1. TRIBULUS. 

 Ovary lG-12-celled , each cavity without transverse septa : fruit unarmed : seed 



solitary. 2. KALLSTROEMIA. 



Shrubs or trees : seeds with hard endosperm. 



Ovary sessile : fruit pubescent : carpels indehiscent. 3. COVILLEA. 



Ovary short-stalked : fruit glabrous : carpels dehiscent. 



Sepals deciduous : filaments without appendages. 4. GUIACUM. 



Sepals persistent : filaments with appendages. 5. PORLIERIA. 



i. TRI'BULUS L. 



Commonly diffuse more or less silky herbs, with weak often prostrate stems and branches. 

 Leaves opposite : stipules narrow. Flowers solitary on axillary pedicels. Sepals 5, im- 

 bricated, deciduous. Disk 10-lobed. Petals 5, imbricated, spreading, white or yellow, 

 fugacious. Stamens 10, inserted below the disk : filaments filiform, naked, the inner 5 

 alternate with the petals, shorter than the outer, each accompanied by a small gland. 

 Ovary sessile, 5-celled, each cavity transversely several-celled : styles united into a short 

 stout column : stigmas 5, nearly parallel. Ovules 3-5 in each cavity, pendulous, anatro- 

 pous. Fruit 5-angled, spiny, at maturity separating into 5 several-seeded carpels, leaving 

 no central axis. Seed solitary in each cavity of the carpels, with a membranous testa. 

 Endosperm wanting. CALTROP. BUR-NUT. 



Pedicels 1-1.5 cm. long : petals shorter than the sepals. 1. T. terrestris. 



Pedicels 2.5-4 cm. long : petals several times longer than the sepals. 2. T. cistoides. 



1. Tribulus terr6stris L. Stems radially branched at the base, the branches pros- 

 trate, 2-11 dm. long, forked : leaves numerous, 2-6 cm. long : leaflets 10-14, the blades 

 oblong or oval, 3-12 mm. long, acute or somewhat apiculate, sessile : flowers on short axil- 



