144 KEY AND FLORA 
52. RUTACEZH. Rue Famity 
Shrubs or trees. Leaves alternate, compound, without stip- 
ules, marked with translucent dots. Flowers usually actino- 
morphic. Sepals and petals 3-5 or none ; petals hypogynous 
or perigynous when present. Stamens as many or twice as 
many as the sepals, inserted on the glandular disk. Pistils 
2-5, often partially united. Fruit a capsule, a key fruit, or in 
the important genus Citrus (orange, lemon, lime, etc., not here 
described) a leathery-skinned berry, the outer part of the skin 
containing many spherical oil cavities.* 
I. XANTHOXYLUM 
Trees or shrubs; bark, twigs, and petioles usually prickly ; 
leaves odd-pinnate, marked with translucent dots. Flowers in 
axillary or terminal cymes or umbels, moncecious or dicecious. 
Sepals and petals 3-5 or none. Stamens 3-5, hypogynous. 
Pistils 2-5, distinct. Carpels 2-valved, 1-2-seeded; seeds 
smooth and shining.* 
1. X. americanum Mill. Nortuern Prickxity Asn, TooTHaAcHE 
Tree. A prickly shrub, 8-12 ft. high, with aromatic bark. Leaves 
pinnately compound; leaflets ovate-oblong. Flowers small and 
greenish, in axillary umbels, appearing before the leaves. Petals 
4-5. Pistils 3-5, the styles slender. Pods rather globose, somewhat 
more than } in. in diameter, roughish, borne on a short stalk above 
the receptacle, with a strong scent of lemon and tasting at first aro- 
matic, then burning. Rocky woods, ravines, and river banks. 
Il. PTELEA L. 
Shrubs with smooth and bitter bark. Leaves with 3 leaflets. 
Flowers in terminal cymes, somewhat monecious. Sepals 3-6, 
deciduous, much shorter than the petals. Stamens 4-5, longer 
than the petals and alternate with them. Pistillate flowers 
producing imperfect stamens. Ovary compressed, 2-celled. 
Fruit a 2-celled, 2-seeded, broadly winged key.* 
1. P. trifoliata L. Hop Tree, Warer Ast. A shrub 4-8 ft. high. 
Leaves long-petioled; leaflets oval or ovate, acute, obscurely serrate, 
