18 Field Manual 



—53— 



■')o. I5a.se of petiole covering the axillar}- bud; twigs with 

 stipnlar rings. Platanus. (47). 



■••".. Axillar}- buds usually eviclcnt; twig> without stijjular 

 rings. ~)4. 



'A. Leaves "i-ranked. b'y. 



•')4. Leaves not 2-ranked. <»'». 



•V). Leaves entire, round-heart-shaped. Cercis. (29). 



')'>. Leaves serrate, dentate, or lobed. 56. 



5(i. I'ith usually in transverse plates; leaves ovate-lance- 

 olate, inequilateral, taper-pointed. Celtis. (50). 



5(1. IMth solid, not diaphragmed. 57. 



57. With milky sap. 58. 



57. Without milky sap. 59. 



5S. Twigs gray or browni glabrous or nearly so; leaves 

 pubescent or glabrous beneath. Morus. (51). 



5S. Twigs grayish-green, downy; leaves tomentose be- 

 neath. Papyrius. (5:)). 



59. Leaves not ine(|uilateral; vascular bundles in base of 

 petiole 3. Betula. (59). 



59. Leaves inequilateral at the base; vascular bundlo in 

 base of petiole several, scattered. Tilia. (20). 



(><'. Leaves more or less star-shaped, with 3-7 long pointed 

 serrate lobes, strongly aromatic when crushed; pith 

 5-angled. Liquidambar. (46). 



lid. Leaves entire or three-lobed, bark spicy-aromatic; in- 

 ternodes very unecjual. Sassafras. (10). 



f.o. Leaves crenate. .>errate, dentate, or lobcd. not star- 

 shaped and not spic^^-aromatic. (il. 



lil. Pith 5-angled; trees usually with roinou.^ l)uds; 

 leaves usually broad based. Populus. ((i4). 



(il. Pith cylindrical or nearly so; usually with prominent 

 typical thorns. Crataegeus. (2(i). 



—62— 



62. Pith diaphragmed, with cavities; large trees with pin- 



nate leaves. Juglans. (62). 

 (i2. Pith not diaphragmed. 63. 



63. Leaves trifoliate, odd-pinnate or odd-bipinnate. 64. 



