BETULACEAE - Birch Family
Deciduous trees and shrubs
Leaves alternate, simple, with
stipules
Flowers unisexual, highly reduced, in catkins, wind-pollinated
Fruit a 1-seeded samara or nut
6 genera, 120 species
Divided into two subfamilies on basis of male flowers:
Betuloideae (male flowers in groups of 3):
Alnus (Alder),
Betula (Birch)
Coryloideae (male flowers solitary):
Carpinus (Hornbeam, Ironwood)
Corylus (Hazelnuts, filberts)
Ostrya (Hop-hornbeam, Ironwood)
Ostryopsis
Economic importance - timber from birches, hazel nuts
Diagnostic characters - deciduous trees or shrubs, leaves serrate,
staminate flowers in catkins,
pistillate flowers in coneline
catkins
Unusual charcteristics - Alnus
(alders) fix nitrogen symbiotically in nodules on roots. The
fixation requires microrganisms that reside in the root nodules. The
only other group of angiosperms that are capable of nitrogen fixation
are legumes
IMAGE GALLERY
FLOWERING
PLANT GATEWAY