540 RUTACEAE 



Fruit a samara; cells of ovary 2-oviiled; trees or shrubs with digitately compound leaves. 



1. Ptelea. 

 Fruit a capsule; cells of ovary 5- or 6-ovuled; undershrubs or low shrubs with simple 

 leaves. 2. Thamnosma. 



1. PTELEA L. Hop-tree, Shrubby Trefoil. 



Unarmed shrubs or trees. Leaves alternate, rarely opposite, 3-foliolate, 

 rarely 4- or 5-foliolate; leaflets entire or toothed, pellucid-punctate. Flowers 

 polygamous, in corymbose or paniculate cymes. Sepals 4 or 5, rarely 6. Petals 

 as many, greenish or yellowish white. Stamens 4 or 5, rarely 6, hj^iogynous, 

 abortive in the pistillate flowers. Gynoecium of 2 or 3 united carpels; ovules 

 2 in each cavity. Fruit a 2-celled or rarely 3-celled samara with reticulate wings, 

 surrounding the body. 



1. P. Baldwinii T. & G. A shrub or small tree, 3-8 m. high; leaflets usually 

 3, narrowly lanceolate to oval or obovate, 1.5-6 cm. long, crenulate or entire, 

 somewhat pubescent beneath; fruit 1-2 cm. long, with thin oblong to nearly 

 orbicular wings. P. angustifolia Benth. P. crenulata Greene. Woods and 

 canons: Fla.— Tex. — Colo.— Calif.; Mex. Son. — Submont. 



2. THAMNOSMA Torr. & Frem. 



Strong-scented glandular shrubs or undershrubs. Leaves simple, alternate, 

 entire. Flowers perfect, racemose. Sepals 4. Petals 4, imbricate. Disk 

 present, cup-like, entire or crenate. Stamens 8, inserted on the disk; filaments 

 subulate or filiform. Gynoecium of 2, rarely 3, united carpels; ovary 2- or 3- 

 lobed; style filiform; ovules 5-6 in each cavity. Capsule leathery, 2- or 3-celled, 

 opening at the apex. 



Shrubbv; corolla 8-10 mm. long; capsule distinctly stipitate. 1. T. montana. 



Herbaceous from a woody base; corolla about 4 mm. long; capsule sessile or subsessile. 



2. T. tcxana. 



1. T. montana Torr. & Frem. A glandular shrub, 3-6 dm. high, often 

 spinose; leaves few, early deciduous, linear to spatulate or oval; petals purple, 

 oblong or oval; filaments filiform; seeds 3 or by abortion solitary. Arid regions: 

 N.M.— s Utah— Nev.— se Calif.; Mex. Son. 



2. T. texana (A. Gray) Torr. A low undershrub, 1-5 dm. high; leaves 

 linear-oblong to narrowly linear, 5-15 mm. long, entire, sessile; sepals ovate or 

 oval, obtuse or retuse; petals oval or elliptic, greenish yellow or whitish, tinged 

 with purple; capsule lobed to the middle, 3-7 mm. high. Rutosma purpurea 

 Woot. & Standi. Arid regions: Tex. — Colo. — Ariz.; Mex. Son. 



Family 73. POLYGALACEAE. Milkwort Family. 



Herbs, or rarely shrubs or trees, with alternate, opposite, or whorled 

 leaves; stipules wanting. Flowers irregular, Sepals 5, free, imbricate, the 

 two inner petaloid, called wings. Petals 5 or 3, the lower one concave, 

 often beaked or crested, called keel, the others more or less united. Stamens 

 usually 8; filaments usually united into a tube, cleft on the back; anthers 

 becoming 1-celled, opening by terminal pores or cracks. Gynoecium 

 usually of 2, rarely 5, united carpels. Fruit usually a 2-celled capsule. 



1. POLYGALA (Tourn.) L. Milkwort. 

 Filaments united. Capsule compressed laterally, 2-celled. Seeds caruncled. 



Plants herbaceous, imarmed; keel with a fimbriate crest. . 



Annuals; leaves verticillate, narrowly linear. 1. P. verticillata. 

 Perennials; leaves alternate. 



Leaves linear or linear-oblanceolate. 2. P. alba. 



Leaves lanceolate to ovate. 3. P. Senega. 

 More or less spiny undershrubs; keel not crested, but with a beak. 



Plant 5-15 cm. high; flowers 7-10 mm. long. 4. P. subspinosa. 



Plant 3-10 dm. high; flowers 3-4 mm. long. 5. P. acanlhodada. 



