cc. Thorns or spines much exceeding V 2 inch in length on 

 the branches. 



d. Thorns usually 'branched, situated above the nodes; 

 lateral buds superposed, the lower covered by bark; 



fruit a flat pod GLEDITSIA, p. 165. 



dd. Thorns unbranched on twigs, situated ,at the nodes; 

 lateral buds not superposed, not covered by bark ; 



fruit a small pome CRATAEGUS, p. 151. 



bb. Twigs, branches or trunks unarmed. 



c. Leaf-scars mainly crowded on short, stout, lateral shoots. 



d. Bundle-scar i ; fruit a cone, usually present 



-LARIX, p. 17. 



dd. Bundle-scars 2; fruit a globose drupe falling in 



autumn ....GINKGO, p. 3. 



cc. Leaf-scars distributed along the lateral branches. 



d. Leaf-scars (or some of them) 3 at a node, i. e., 



whorled CATALPA, p. 223. 



dd. Leaf-scars 1-2 at a node, i. e., not whorled. 

 e. Leaf-scars 2 at a node, i. e., opposite. 



f. Terminal buds ^2-1^2 inches long, resin-coated; 



twigs very stout AESCULUS, p. 195. 



ff. Terminal buds rarely exceeding ^ inch in length, 

 not resin-coated ; twigs not conspicuously stout, 

 g. Leaf buds with i pair of scales visible, 

 h. Buds scurfy-pubescent.. VIBURNUM, p. 229. 



hh. Buds glabrous OORNUS, p. 203. 



gg. Leaf buds with 2 or more pairs of scales visible, 

 h. Bundle-scars usually 3, distinct, separated.. 



ACER, p. 174. 



hh. Bundle-scars many, minute; more or less con- 

 fluent in a U-shaped line 



FRAXINUS, p. 211. 



ee. Leaf-scars i at a node, i. e., alternate, 

 f. Bundle-scars 1-3. 



g. Bundle-scar only i, or appearing as i. 

 'h. Twigs bright green, spicy-aromatic; bundle- 

 scar appearing as a horizontal line ; terminal 



bud present ; pith homogeneous 



, SASSAFRAS, p. 139. 



XXVIII 



