Common Name: 

About 9 species of deciduous trees.  Leaves simple, alternate, in two rows, parallel veins, margins serrate or dentate.  Male flower catkins are Carpinus- or Betula-like, but form in fall.  Female flowers in terminal short spikes or catkins, 3-12 pairs of flowers, each pair subtended by a bract and each flower in a sac-like husk, which inflates on fruiting giving the cluster a hop-like appearance.  Native to Europe, Asia, and North America.
Ostrya: Greek for shell, a reference to the inflated husk of the fruit.

Betulaceae, Carpinaceae