Key to Ulmaceae
1a. Fruit dry samara; flowers bisexual
   2a.  Flowers bisexual; fruit symmetric, winged on both sides; branchlet without spines        Ulmus
   2b. Flowers polygamous; fruit asymmetric, winged only on one side; branchlet with spines Hemiptelea
1b. Fruit a drupe; flowers unisexual or polygamous
   3a. Leaves palmately 3-nerved from base; winter bud scales 6-10 or 2-6
     4a. Flowers unisexual; lateral nerves of leaves straight, ending in the teeth; winter bud sacled 6-10                 Aphananthe
     4b. Flowers polygamous; lateral nvers of leaves arcuate near the margin, not ending in the theeth; winter bud scaled 2-6 Celtis
   3b. Leaves pinnately nerved; winter bud scales 8-10                                                                                            Zelkova