d. Trunk and large branches armed with stout spines; 

 leaflets &-i5^ inches long. . . . . . .GLEDITSIA, p. 165. 



dd. Trunk and large branches unarmed ; leaflets 2-2^/2 



inches long GYMNOCLADUS, p. 163. 



bb. Leaves opposite. 



c. Leaves pinnately compound; fruit a samara. 



d. Leaflets 3-5 ; samaras paired ACER, p. 172. 



dd. Leaflets 7-11, exceptionally 5; samaras not paired 



FRAXINUS, p. 210. 



cc. Leaves digitately compound ; fruit a prickly bur 



AESCULUS, p. 194. 



XXVI 



