^6 Proceedings of flic Ohio State Academy of Science 



most" cases pubescent; some sjiecies with cliaracteristic 

 transverse self-pruning scars on the twigs, others with 

 corky ridges. Ulmus. (23). 

 2,y. Bark scaly, fine-furrowed, the furrows usually somewhat 

 spiral ; bud scales green with l)rown ti])s, nearly 

 glabrous; staminate catkins exposed in winter. 



Ostrya. (17). 



37. Bark of trunk and larger l^ranches separating into papery 



or leather}- sheets: catkins in winter. Betula. (18). 



-38- 



38. With 2 or more superposed axillary buds; all except 



I may be very small. 39. 



38. Axillary buds single or 2 or more side by side ; not 



superposed. 46. 



39. Pith diaphragmed. with air cavities. 40. 



39. Pith diaphragmed but solid ; bundle scars 3 ; stipular 

 scars none. Nyssa. (76). 



39. Pith not diaphragmed, solid. 41. 



40. Pith large, brown ; twigs thick, with large leaf scars 



and 3 prominent bundle scars. Juglans. (14). 



40. Pith rather small, white or greenish ; leaf scars semi- 



circular : outer bud scales about 2. 



Mohrodendron. (68). 



41. Buds partly sunken, hardly projecting beyond the sur- 



face ; terminal bud self-pruned or tips of branches 

 withering. 4.2. 



41. Buds not sunken in the epidermis. 43. 



42. Leaf scar not surrounding the axillary buds ; pith large, 



chocolate-colored : twigs robust, polished, mottled 

 white and purplish-brown. Gymnocladus. (46). 

 42. Leaf scar surrounding the Axillary buds, quadrangular 

 L'-shaped : bark with pungent odor; pith white. 



Ptelea. (50). 



42. Leaf scar covering the axillary buds; pith small; twigs 



brown, polished, often zigzag. Gleditsia. (45). 



43. Pith cylindrical or nearly so. 44. 



