1911 Encyclopædia Britannica/Cupuliferae
CUPULIFERAE, a botanical order, or, in recent arrangements, group of orders, containing several familiar trees. The plants are trees or shrubs with simple leaves alternately arranged and small unisexual flowers generally arranged in catkins and pollinated by wind-agency. The generally one-seeded nut-like fruit is associated with the persistent often hardened or greatly enlarged bracts forming the so-called cupule which gives the name to the group. The group is subdivided as follows, and these subdivisions are now generally regarded either as distinct natural orders or the first two as sub-orders of one natural order.
Betuleae or Betulaceae. Female flowers arranged, two to three together on scale-like structures formed by the union of bracts, in catkins; ovary two-celled; fruit small, flattened, protected between the ripened scales of the catkin. Includes Betula (birch) and Alnus (alder).
Coryleae or Corylaceae. Female flowers in pairs, the bracts enlarging in the fruit to form a membranous cup (hazel), or a flat three-lobed structure (hornbeam). Ovary two-celled. Includes Corylus (hazel) and Carpinus (hornbeam).
Fagaceae (Cupuliferae in a restricted sense). Bracts forming a fleshy or hard cupule which envelops the one to several fruits. Ovary three-celled. Includes Quercus (oak), Fagus (beech), Castanea (sweet-chestnut).