144 KEY AND FLORA 



52. RUTACE^. Rue Family 



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, monoecious or dioecious. 

 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. Northern Prickly Ash, Toothache 

 Tree. A prickly shrub, 8-12 ft. high, with aromatic bark. Leaves 

 piniiately 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. 



II. PTELEA L. 



Shrubs with smooth and bitter bark. Leaves with 3 leaflets. 

 Flowers in terminal cymes, somewhat monoecious. 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, Wafer Ash. A shrub 4-8 ft. high. 

 Leaves long-petioled ; leaflets oval or ovate, acute, obscurely serrate, 



