63 



GENERAL KEY TO THE FAMILIES. 



Page. 



1. Leaves narrow, needle-like, awl- like, or scale-like, usually persistent except in the 



genus Larix, Pinaceae 67 



1. Leaves broad, flat, rarely five times as long as wide, usually deciduous, 2 



2. Leaves opposite or whorled, i. e., two or three occur at a node, 3 



2. Leaves alternate, i. e. f only one occurs at a node, 10 



3. Leaves, or at least most of them, three at a node Bignoniaceae 211 



3. Leaves always two at a node 4 



4. Leaves simple 5 



4. Leaves compound 8 



5. Leaves palmately lobed, Aceraceae 190 



5. Leaves not lobed, 6 



6. Leaves serrate, Viburnum in Caprifoliaceae 218 



6. Leaves entire, 7 



7. Leaves 3-6 inches long with curving parallel veins; bases of leaf stalks enlarged, 



encircling twigs, Cornus in Gornaceae 204 



7. Leaves 4-8 inches long without curving parallel veins; bases of leaf stalks do not en- 



circle twigs Chionanthus in Oleaceae 217 



8. Leaves palmately compound Sapindaceae 200 



8. Leaves pinnately compound, 9 



9. Leaflets usually 5-11; finely toothed or entire margined, Fraxinus in Oleaceae 212 



9. Leaflets usually 3, sometimes 5-lobed or coarsely serrate, ..Acer Negundo in Aceraceae 197 



10. Leaves simple, 11 



10. Leaves compound, 40 



11. Leaves persistent 12 



11. Leaves deciduous 14 



12. Leaves not armed with spiny teeth, 13 



12. Leaves armed with spiny teeth, Ilex opaca in Aquifoliaceae 188 



13. Small trees; leaves stout, white silky beneath, not taper pointed; flowers soli- 



tary, ..' Magnolia virginiana in Magnoliaceae 156 



13. Shrubs; leaves leathery, yellowish-green to scurfy beneath, often taper pointed; 



flowers in clusters, Rhododendron and Kalmia in Ericaceae 207 



14. Leaves with entire margins, 15 



14. Leaves with toothed, lobed, or incised margins, 23 



15. Leaves broadly heart-shaped; flowers reddish-purple, shaped like pea blossoms; fruit 



a pea-like pod, Cercis in Leguminosae 180 



15. Leaves not broadly heart-shaped; flowers not shaped like pea blossoms; fruit not 



a pea-like pod, 16 



16. Stout axillary spines present; fruit 3-5 inches in diameter, Maclura in Urticaceae 153 



16. Stout axillary spines absent; fruit smaller 17 



17, Leaves decidedly aromatic, often somewhat lobed; twigs spicy-aromatic, mucilagin- 



ous if chewed Lauraceae 161 



17. Leaves not aromatic or lobed; twigs not spicy-aromatic, nor mucilaginous, 18 



18. Leaves 2-G inches long; flowers small except pistillate of Diospyros, not soli- 



tary, 19 



18. Leaves more than 6 inches long; flowers large and solitary 22 



19. Leaves bristle-tipped, linear-lanceolate to oblong; pith star-shaped; fruit an acorn.... 



Quercus imbricaria and Q. phellos in Fagaceae 146 



19. Leaves oval-ovate or obovate, not bristle-tipped; pith not star-shaped; fruit a drupe 

 or a berry, 20 



