TREES xv 



30. Internodes elongated. Libocedrus. 

 Internodes about as 1 broad as long. 31. 



31. Internodes narrow (1-1.5 mm.). p. 14. Chamaecyparis. 

 Internodes distinctly broader. 32. 



32. Internodes 2-4 mm. wide: seeds 2. p. 12. Thuja. 

 Internodes broader: seeds numerous. p. 13. Thujopsis. 



Deciduous Trees. 



33. Armed with at least some spines or prickles. 34. 

 Unarmed. 46. 



Armed. 



34. Leaves alternate, never 4-ranked. 35. 

 Leaves opposite, or 4-ranked if alternate. 45. 



35. With prickles only. 36. 



With thorns occupying the place of stipules. 38. 

 With pungent twigs or spurs. 40. 



36. Leaves digitate or digitately lobed. p. 112. Acanthopanax. 

 Leaves bipinnate. p. 112. Aralia. 

 Leaves once pinnate. 37. 



37. Armed only when young. p. 80. Ailanthus. 

 Prickles persistent. p. 79. Zanthoxylum. 



38. Leaves pinnately compound: thorns detachable. 



Pellucid-dotted. p. 79. Zanthoxylum. 



Not pellucid-dotted. p. 74. Robinia. 



Leaves simple: thorns firm. 39. 



39. Glabrous: fruit dry, winged. p. 98. Paliurus. 

 Pubescent: fruit drupe-like. p. 98. Zizyphus. 



40. Leaves simple. 41. 



Leaves both pinnate and bipinnate. p. 69. Gleditsia. 



41. With silvery or brown peltate scales. p. 107. Elaeagnus. 

 Not scurfy. 42. 



42. Sap milky. p. 30. Maclura. 

 Sap not milky. 43. 



43. With nectar-glands on leaf-base or petiole, p. 67. Prunus. 

 Leaves without nectar-glands: fruit a pome. 44. 



44. Bud-scales thin: core of fruit papery. p. 56. Pyrus. 

 Bud-scales fleshy: core of fruit bony. p. 60. Crataegus. 



45. With silvery or brown peltate scales, p. 107. Shepherdia. 

 Not scurfy: spines short, terminal. p. 97. Rhamnus. 



