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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 alternifolia in Cornaceae 205 



20. Leaves thicli, 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 fibro-vascular bundle; fruit a globular 



berry inches in diameter, Ebenaceae 210 



21. Leaves 2-5 inches long; leaf petioles with 3 fibro-vascular bundles; fruit 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-lilie; twigs often aromatic and bitter, Magnoliaceae 155 



22. Stipules absent; flowers reddish-purple, ill-smelling; fruit banana-lilie, edible; twigs 



not aromatic or bitter, Anonaceae 



23. Leaf margins usually lobed or incised, 24 



23. Leaf ma.rgins usually toothed 29 



24. Leaves star-shaped, Liquidambar in Hamamelidaceae 163 



24. Leaves not star-shaped, 25 



25. Leaves silvery beneath Populus alba in Salicaceae 94 



25. Leaves not silvery beneath 26 



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



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



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



Lauraceae 



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



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



Platanaoeae 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 TJrticaceae 



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 162 



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



fruit with bract, Tiliaceae 202 



32. Leaves dentate or coarsely toothed, 33 



. 32. Leaves not dentate nor coarsely toothed, 34 



33. Leaves with laterally flattened petioles, Populus grandidentata 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 tuft of hairs at 



apex; flowers monoecious; calyx present, Betulaceae 111 



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



flowers dioecious; calyx absent, Salicaceae 



37. Thorns or spine-like spurs present, 



Prunus americana, Pyrus coronaria, and Crataegus sp. in Rosaceae 164 



37. Thorns or spine-like spurs not present 38 



38. Fruit with a single stone, Prunus in Rosaceae 



38. Fruit several-seeded, 39 



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



Amelanchier in Rosaceae 



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

 one to few flowered axillary clusters, Ilex monticola in Aquifoliaceae 



