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20. Leaves thin, clustered at tip of twigs, with prominent curved parallel veins; small 



trees; twigs greenish streaked with white Cornus alternifoUa in Cornaceae 205 



20, Leaves thick, not clustered at the tip of twigs; veins not parallel; medium sized 



trees; twigs not greenish, 21 



21. Leaves 4-6 inches long; leaf petioles with one flbro-vascular bundle; fruit a globular 



berry 1-li inches in diameter, Ebenaceae 210 



21. Leaves £-5 inches long: leaf petioles with 3 fibro-vascnlar bundles: fniit a purple 



ovoid drupe | of an inch long Nyssa in Cornaceae 206 



22. Stipules and stipule-scars encircle twigs; flowers greenish-white or yellowish: fruit 



cone-like; tAvigs often aromatic and bitter, MagnoUaceae 155 



22. Stipules absent: flowers reddish-purple, lU-smelling; fruit bauana-like. edible: twigs 



not aromatic or bitter, Anonaceae IGO 



23. Leaf margins usually lobed or incised, 24 



23. Leaf margins usually toothed 29 



24. Leaves star-shaped Liquidamhar in Hamamelidaceae 163 



24. Leaves not star-shaped 25 



25. Leaves silvery beneath Populus alba in Salicaoeae M 



25. Leaves not silvery beneath 26 



26. Leaves rough on upper surface, with milky juice, Morus in Urticaceae 154 



26. Leaves not rough on upper surface, without milky juice, 27 



27. Leaves decidedly aromatic, lobed or entire; twigs spicy-aromatic, mucilaginous 



Lauraceae 161 



27. Leaves not aromatic; twigs not spicy -aroma tic nor mucilaginous 28 



28. Leaves palmately veined; base of leaf petioles hollow; leaf lobes Irregularly toothed. 



Platanaceae 175 



28. Leaves pinnately veined; base of leaf petioles not hollow; leaf lobes rounded or 



bristle-pointed, intervening spaces deep or shallow Most species in Fagaceae 124 



29. Leaves with an oblique base 30 



29. Leaves not with an oblique base, 32 



30. Leaves ovate or ovate-oblong; rough on upper surface, Ulmus and Celtis In ITrticaceae 14S 



30. Leaves rounded, heart-shaped, or obovate; smooth on upper surface 31 



31. Leaves straight- veined with wavy margins; flowers in late autumn; fruit without bract. 



Hamamelis in Hamamelidaceae 1C2 



31. Leaves not straight veined, deeply and sharply toothed; flowers appear in summer; 



fruit with bract Tiliaceae 202 



32. Leaves dentate or coarsely toothed, 38 



32. Leaves not dentate nor coarsely toothed 34 



33. Leaves with laterally flattened petioles, Populus grandldentata in Salicaceae 97 



33. Leaves not with laterally flattened petioles, Few species in Fagaceae 124 



34. Fruit dry 35 



34. Fruit fleshy 37 



35. Leaves decidedly sour: flowers and fruit produced in racemes resembling the lily of 



the valley Oxydendrum In Ericaceae 209 



35. Leaves not sour; flowers and fruit not produced in racemes 36 



36. Fruit 1-seeded. nut or samara, subtended by bracts; seeds without tnft of hairs at 



ape.v ; flowers monoecious ; calyx present, Betnlaceae 111 



36. Fruit a small capsule inclosing numerous seeds; seeds with tuft of hairs at apes; 



flowers dioecious: calyx absent, Salicaceae S8 



37. Thorns or spine like spurs present 



Frunus americana, Pyrus coronaria, and Crataegus sp. in Bosaceae 164 



37. Thorns or spine-like spurs not present 38 



38. Fruit with a single stone, Prunus in Sosaceae Ite 



38. Fruit several-seeded, 39 



39. Leaves heart-shaped or rounded at base, 3-4 inches long; flowers in loose racemes, 



Amelanchier in Sosaceae 174 

 39. Leaves wedge-shaped or rounded at the base, 4-5 inches long; flowers solitary or in 



one to few flowered axillary clusters, Hex monticola in Aquifoliaceae 189 



