86 
Spring Flora of Oklahoma 
1. Cathartolinum rigidum (Pursh.) Small. Large-flowered 
Yellow Flax. Glabrous or puberulent, 6'-15' high. Leaves linear 
or linear-lanceolate 4"-12" long. Glandular-serrulate or ciliate 
Flowers yellow, 9"-15" broad. Capsuie ovoid, 5-valved, shorter than 
the sepals, 2"-2*4" long. 
Prairies. May-July. 
2. Cathartolinjum Berlandieri (Hook.) Small. Berlandier’s 
Yellow Flax. Bright green, glaucescent, perennial, stem 3'-16' 
high. Leaves linear or linear-lanceolate, 7"-20" long. Flowers 
bright yellow, 16"-24" broad. Sepals evenly glandular-toothed. Pet¬ 
als obovate. Capsule ovoid, 2"-2t4" long. 
In dry soil. April-June. 
FAMILY 43. ZYGOPHYLLACEiE. Caltrop Family. 
Trailing herbs or spreading shrubs, with compound 
leaves, 2-several-foliolate, abruptly-pinnate leaves. Leaf¬ 
lets small, entire. Flowers perfect, yellow or orange, 
rather small, regular. Sepals 5. Petals 5. Stamens twice 
as many, in 2 whorls. Pistil of 5 united carpels. Fruit a 
capsule of various forms, 3-12-celled, separating at ma¬ 
turity into nutlets containing the seed. 
Fruit with several strong sharp spines. I. Tribulus. 
Fruit merely tuberculate, not spiny. II. Kallstroemia. 
I. TRIBULUS (Torun.) L. 
Prostrate herbs with evenly-pinnate stipulate leaves 
and axillary flowers. Sepals 5, deciduous. Petals 5, de¬ 
ciduous. Stamens 10, hypogynous, the alternate ones 
somewhat longer. Ovary sessile, 5-lobed, 5-celled, hairy. 
Fruit 5-angled, spiny, splitting into five 3-5-seeded seg¬ 
ments. 
1. Tribulus terrestris L. Ground Burnut. Annual pubescent, 
the stem prostrate, sometimes 12' long or more. Leaflets 4-8 pairs, 
oblong, inequilateral, opposite, 3"-8" long. Flowers solitary, about 
6" broad. Peduncles shorter than the leaves. Petals oblong, about 
as long as the sepals. Segments of the fruit each with two stout 
spines and two or more smaller ones. 
