28. 
TREES. ; : 13 
Leaves alternate. 
With prickles. 20. 
With thorns occupying the place of stipules. 31. 
With pungent twigs or spurs. 33. 
29. Leaves digitately lobed or digitate. Acanthopanax. 
Leaves once pinnate. 30, 
Leaves bipinnate. Aralia. 
30. Armed only when young. Ailanthus. 
Older branches armed. Zanthoxylum. 
31. Leaves pinnately compound: thorns detachable. Robinia. 
Leaves simple: thorns firm. 32. 
32. Glabrous: fruit dry, winged. Paliurus. 
Pubescent: fruit fleshy, drupe-like. Zizyphus. 
33. Leaves simple. 34. 
Leaves unequally pinnate or bipinnate. Gleditsia. 
34. With silvery or brown peltate scales. Elaeagnus. 
Not’scurfy. 35. 
35. Sap milky: fruit like a great mulberry. Maclura. 
Sap not milky. 36. 
36. Leaves with nectar-glands on petiole or base. Prunus. 
Leaves without nectar-glands. 37. 
37. Pome with papery core: bud-scales thin. Pyrus. 
Core of fruit bony: bud-scales fleshy. Crataegus. 
Leaves opposite. 
38. With silvery or brown peltate scales. Shepherdia. 
Not scurfy: spine short, terminal. Rhamnus. 
Deciduous Trees—Unarmed. 
39. Leaves alternate or clustered on alternate spurs. 40. 
40. 
Leaves opposite, or 4-ranked if separated. 104. 
Leaves whorled, 3 at a node, large. Catalpa. 
Leaves alternate. 
Leaves small and very narrow: fruit a cone. 41. 
Leaves comparatively large: fruit not a cone. 43. 
