Firs (''Abies'') are a genus of 48–56 species of evergreen coniferous trees in the family Pinaceae. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range. Firs are most closely related to the genus ''Cedrus'' (cedar). Douglas firs are not true firs, being of the genus ''Pseudotsuga''.
They are large trees, reaching heights of tall and trunk diameters of when mature. Firs can be distinguished from other members of the pine family by the unique attachment of their needle-like leaves and by their different cones.
Identification of the different species is based on the size and arrangement of the leaves, the size and shape of the cones, and whether the bract scales of the cones are long and exserted, or short and hidden inside the cone.
Firs can be distinguished from other members of the pine family by the unique attachment of their needle-like leaves to the twig by a base that resembles a small suction cup.
The leaves are significantly flattened, sometimes even looking like they are pressed, as in ''A. sibirica''.
The leaves have two whitish strips on the bottom, each of which is formed by wax-covered stomatal bands. The upper surface of the leaves usually is uniformly green and shiny, without stomata or only with few at their tips, visible as whitish spots. Some of the species however have the upper surface of leaves dull, gray-green, bluish-gray to silvery, coated by wax with variable number of stomatal bands, and not always continuous. An example species with shiny green leaves is ''A. alba'', and an example species with dull waxy leaves is ''A. concolor''.
The tips of leaves are usually more or less notched (as in ''A. firma''), but sometimes rounded or dull (as in ''A. concolor'', ''A. magnifica'') or sharp and prickly (as in ''A. bracteata'', ''A. cephalonica'', ''A. holophylla''). The leaves of young plants are usually sharper.
The way they spread from the shoot is very diverse, only in some species comb-shaped, with the leaves arranged on two sides, flat (''A. alba'') 〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』