1. Leaves even-pinnately lobed, with 4 (or sometimes 6 or 8) lobes, apex a very broad V-notch or truncate…Liriodendron
1. Leaves odd-pinnately lobed, with 3, 5, 7, etc. lobes (or sometimes with 2 lobes, but one obviously central and the other smaller and to the side, mitten-like), the apex obtuse to acute…2.
2. Leaf lobe margins entire…3.
3. Leaves deeply 2- or 3-lobed (or rarely with 1-4 additional very small, tooth-like lobes towards the base), most branches with a
mixture of unlobed, 2-lobed (mitten), and 3-lobed leaves; fruit a blackish-seeded drupe; fresh plants strongly aromatic…Sassafras
3. Leaves shallowly or deeply 3-25-lobed; fruit either an acorn or a rather fleshy spherical multiple fruit; fresh plants not aromatic…4.
4. Leaves shallowly or deeply 3-25-lobed; fruit a nut in a cupule (an acorn); trees unarmed…Quercus
4. Leaves shallowly 3-lobed (or mostly unlobed); fruit a rather fleshy multiple fruit; trees armed…Maclura
2. Leaf lobe margins serrate…5.
5. Leaves irregularly toothed, the teeth tipped by a soft bristle; fruit a nut in a cupule (an acorn); small to large trees…Quercus
5. Leaves evenly and rather finely serrate, not bristly-tipped; fruit at least somewhat fleshy, either a pome or a multiple of nutlets
surrounded by a fleshy calyx; small trees…6.
6. Petals 5, conspicuous, white or pink; fruit a pome; leaves mainly small, generally < 8 cm long; trees armed…Crataegus
6. Petals absent (the individual flowers inconspicuous and aggregated into catkins); fruit a multiple, of nutlets surrounded by a fleshy calyx (mulberry) or a syconium (fig); leaves mainly larger, at least some on a branch > 8 cm long; trees unarmed…7. [Moraceae]
7. Stipules connate, stipule scar encircling the twig; inflorescence a syconium (the flowers borne on the inner walls of the fleshy receptacle)…Ficus
7. Stipules free, stipule scar not encircling the twig; inflorescence a spike, head, or catkin (the flowers borne exposed on a contracted or elongated axis or receptacle)…8.
8. Stems and leaves hirsute; leaves alternate, opposite, and whorled…Broussonetia
8. Stems and leaves glabrous to pubescent; leaves alternate…Morus
