674 RUTACEAE 
Gynoecium 2-carpellary `” leaf-blades entire. 2. THAMNOSMA. 
** Ovules 2 in each cavity : capsule not lobed, 2-5 together. 
Calyx wanting. 3. XANTHOXYLUM. 
Calyx present. 4. FAGARA. 
b. Fruit indehiscent, samaroid. 
Filaments glabrous: fruit separating into3-4 carpels which are winged on the 
back. 5. HELIETTA. 
Filaments pubescent : fruit winged all around. 6. PTELEA. 
B. Fruit a pulpy drupe or a berry. 
Stamens 8: fruit a drupe: leaf-blades 3-5-foliolate. 7. AMYRIS. 
Stamens 20-60 : fruit à berry : leaf-blades 1-foliolate. 8. CITRUS. 
1. RUTA L. 
Perennial caulescent sometimes partly woody herbs, with glandular-punctate foliage 
and often heavy scented herbage. Leaves alternate : blades divided. Flowers in terminal 
corymbose or panicled cymes. Sepals 4-5, persistent. Petals 4-5, yellow or greenish, 
imbricated. Disk thick, 8-10-lobed. Stamens 8-10. Ovary 4-5-celled, sessile, 4-5- 
lobed: styles united: stigma terminal. Ovules several in each cavity of the ovary. 
Capsule 4—5-celled, 4—5-lobed, commonly opening at the apex. Seeds several. 
1. Ruta gravéolens L. Stems 2-8 dm. tall, corymbose at the ends : leaf-blades twice 
ternately divided, the ultimate segments rounded or notched at the apex : sepals triangular 
or ovate, 2.4-4 mm. long: petals 5-7 mm. long, the broad blade with involute margins and 
apex, abruptly narrowed into the claw : capsules depressed, 8-11 mm. wide, 4—5-lobed. 
In waste places and cultivated grounds, eastern United States. Native of Europe. Spring to fall. 
2. THAMNOSMA Torr. & Frem. 
Strong-scented shrubs or shrubby herbs, usually densely glandular. Leaves alternate: 
blades simple, narrow, entire, often reduced to scales. Flowers perfect, regular, in racemes 
or racemose cymes. Sepals 4. Petals 4, yellow or purplish, sessile, often erect. Disk 
cup-like, entire or crenate. Stamens 8: filaments subulate or filiform. Ovary 2-celled, 
2-lobed, long-stalked or nearly sessile : styles united: stigma capitate. Ovules 5-6 in each 
cavity. Capsule leathery, 2-celled, 2-lobed, opening at the apex. Seeds 4-6, nearly reni- 
form. Testa crustaceous, smooth or rough. Embryo curved. 
1. Thamnosma Texana (A. Gray) Torr. A low partially herbaceous shrub, 1-5 dm. 
tall. Stems much branched, wiry, often densely glandular: leaf-blades linear or linear- 
oblong, 5-10 mm. long, obtuse, more or less glandular-punctate, entire, sessile or nearly so, 
early deciduous: flowers in terminal interrupted racemes: pedicels 1-2 mm. long: calyx 
about 2 mm. broad : sepals ovate, obtuse : petals yellow or purplish, elliptic, oblong-ellip- 
tic or oval, 2.5-3 mm. long, obtuse, slightly involute: stamens shorter than the petals : 
filaments glabrous, subulate : capsules short-stalked, 5-6 mm. high, 2-lobed, the valves ex- 
tending to the middle: seeds nearly 2 mm. broad, flattened, tuberculate. 
On plains and prairies, Texas to New Mexico and Mexico. Spring to fall. 
3. XANTHOXYLUM!' L. 
Aromatic, often prickly, shrubs or trees, with relatively smooth stems. Leaves alter- 
nate: blades pinnately compound : leaflets with more or less pellucid-punctate, entire or 
toothed blades. Flowers greenish yellow, polygamous, in axillary cymes. Sepals want- 
ing. Petals 4-5. Stamens 4-3, abortive in pistillate flowers. Carpels 1-5, short-stalked, 
l-celled, oblique: styles distinct, or united above. Ovules 2 in each cavity. Capsular 
fruit a single carpel or 2-5 carpels together, not lobed, glandular-punctate, 2-valved. 
Seed solitary, finally exserted. i 
1. Xanthoxylum Americànum Mill. A prickly aromatic shrub, with spreading 
branches. Leaf-blades pinnately-compound, 1-3 dm. long, the rachis nearly terete : leaf- 
lets ovate or oblong or rarely oval, 4-8 cm. long, obtuse or short-acuminate, deep green 
above, paler and more or less pubescent beneath, crenate with flat-topped teeth, sessile or 
short-petioled : calyx wanting: flowers in sessile clustered cymes on the wood of the pre- 
vious season, slender-pedicelled : corolla yellowish and greenish, 3-3.5 mm. broad : = 
sules globose or ellipsoidal, 5 mm. in diameter, wrinkled and glandular-punctate : see 8 
ovoid, 4 mm. long, black, shining. 
On river banks and in woods, Quebec and Ontario to Minnesota, Georgia, 
Spring. PRICKLY ASH. TOOTHACHE-TREE. 
Missouri and Nebraska. 
Originally spelled ZANTHOXYLUM. 
