Flowers: Imperfect and the plants monoecious, tiny; actinomorphic; carpels 2, syncarpous; ovary usually inferior (hard to see this), 2-locular below but 1-locular above, 1 pendulous ovule per locule near top of partition

Inflorescence: Staminate flowers in 2-3 flowered cymules subtended by bracts, clustered into catkins. Carpellate flowers in 1-3 flowered cymules subtended by bracts, clustered into catkins, these sometimes cone-like

Fruits: Nuts and samaras, 1-seeded

Habit: Trees and shrubs, mostly of cooler parts of Northern Hemisphere

Leaves: Alternate, simple, toothed, often with oblique leaf base, stipules present

Examples:

• Alnus (alders)
  
• Betula (birches) B. papyrifera
  
• Carpinus (hornbeams)
  
• Corylus (hazelnuts, filberts)
  
• Ostrya (hop-hornbeams)