cc. Thorns or spines much exceeding J^ 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. I.eaf-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 l /2-iY2 inches long, resin-coated ; 



twigs very stout AESCULUS, p. 195. 



ff. Terminal buds rarely exceeding l / 2 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 CORN US, p. 20.3. 



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. 



xxvni 



