Trkks ()I- thk N'oKTiiKkN Unitki) States 27 



• 17. r.ark scaly. liiu-Uirrow cd, ihc furrows usually sonif- 



wliat >])iral: bud scales «^recu with brown tips, 

 marly .glabrous; twigs glandular-bristly; staminatc 

 catkins cxi)()scd in winter. Ostrya. (.^S). 

 ;!7. r.ark <>{ trunk and larger branclu's sc])arating into 

 l)aiH-ry nr leathery sheets; catkins in winter. 



Betula. (59). 

 —38— 



• ?S. With - i»r more >u])eri)()scd axillary buds: all excei)t 



1 ma\- be ver}- small. •>!>. 



• is. .\xillary buds single or 2 or mnvv side by side; not 



superposed. 4(1. 



■^!'. I'ith diai)hragmed. with air ca\itie>. h>. 



■'!*. rith (liaphragmed but solid: bundle scars •"{; stipular 

 scars none. Nyssa. (Si ). 



:!l». I'ith n..i diaphragmed. >olid. il. 



I<». rith large, brown: twigs thick, with large leaf scars 

 and '] jiromincnt bundle scars. Juglans. (62). 



hi. rith rather >mall. white or greenish; leaf scars semi- 

 circular; outer bud scales about 2. Halesia. (72). 



11. r.uds partly sunken, hardly projecting beyond the sur- 



face; terminal bud self-i)runed (^r tips of branches 

 withering. 42. 



41. Iluds not sunken in the epidermis. h">. 



42. Leaf soar not surrounding tlu' axillary buds: pith 



large, chocolate-colored; twigs robust. i)olishe(l. 

 mottled white and i)nrplish-br. .w n. 



Gymnocladus. i '.! ) 



12. Leaf sc.ir surrounding the axillary buds. (|uadran- 



gular I'-shaped; bark with i)migent odor: pith 



white. Ptelea. ( IS). 

 42. Leaf scar covering the axillary buds; i)ith small: twigs 



brown, polished, often zigzag. Gleditsia. (.Id). 

 I-'!. I'ith e>Iindrical or nearly so. 11. 

 I"'. I'lth m-iic i.r less o-angled. yellowish or brownish; 



lermin.il bud large; bundle scars scattered; trees 



with tom^h twigs. Hicoria. (til). 



