.= Not included in the above. (=O.=)

=O.= Leaves 3 or more times as long as wide, widest near
the center; fruit a round, prickly bur with 1-3
horny-coated nuts 89. _Castanea._

=O.= Leaves widest near the sharply serrate tip, narrow
and entire near the base; fruit small pods in
terminal racemes; small tree or shrub 53. _Clethra._

=O.= Leaves widest near the base, usually small; bark
scaling off like the Buttonwood; fruit axillary,
solitary, small (1/4 in.) roundish, dry drupes. A
cultivated species, has rather large leaves, widest
near the center 75. _Planera._

=P.= Fruit an open oval woody catkin or cone, remaining on
the plant through the winter 84. _Alnus._

=P.= Fruit a rounded stony nut, in green leafy edged bracts;
shrubs or small trees 85. _Corylus._

=Q.= Usually aromatic; bark dotted on the spray and with
horizontal marks on the trunk, peeling off in thin,
often papery layers 83. _Betula._

=Q.= Bark not peeling off in thin layers. (=R.=)

=R.= Leaf-buds long and slender; fruit a small prickly bur
with two triangular, horny-coated nuts; large trees
90. _Fagus._

=R.= Fruit an elongated catkin with large leaf-like bracts;
bark close, gray, on a grooved trunk 87. _Carpinus._

=R.= Fruit a hop-like catkin; bark brownish, finely furrowed
86. _Ostrya._

=S.= Plant more or less thorny; shrub or small tree;
fruit rounded berries ending in persistent
calyx-lobes 38. _Crataegus._

=S.= Plant not thorny. (=T.=)

=T.= Leaf deeply pinnatifid, usually with the basal lobes
completely separated; cultivated 37. _Pyrus._

=T.= End of leaf as though cut off; sides with one large
lobe; margin entire; large tree 2. _Liriodendron._

=T.= Lower leaves three-lobed, heart-shaped at base, upper
merely ovate, margin entire; small tree or shrub
66. _Clerodendron._

=T.= Not as above; leaves usually many-lobed. (=U