Pinaceae
1. Leaves in clusters of 2 to many === 2
1. Leaves solitary === 4
2. Leaves in clusters of 2-6, scaly-sheathed at base (at least when young). Persistent === Pinus
2. Most leaves in clusters of 10-60, not sheathed at base === 3
3. Leaves deciduous. Cones < 40 mm long ==== Larix
3. Leaves persistent. Cones > 40 mm long === Cedrus
4. Leaf scars circular, slightly depressed (not projected at all). Leaf apex notched === Abies
4. Leaves inserted on slightly to conspicuously raised projections (never inserted in a depression). Leaf apex acute to obtuse, never notched === 5
5. Leaves abruptly narrowed to petiole-like base (semi-petiole appressed to the twig, more or less twisted). Leaf margins irregularly and minutely spinulose (high magnification!). Female cones less than 30 mm long === Tsuga
5. Leaves not petiolate or petiole oblique to patent, not appressed to the twig. Leaf margins entire. Female cones longer than 30 mm === 6
6. Leaves borne on peg-like, long decurrent projections (twigs roughened after leaves fall). Smell resinous === Picea
6. Leaves borne on slightly raised, elliptic, non-decurrent projections (twigs not or hardly roughened after leaves fall). Smell of apple === Pseudotsuga
Literature:
Christensen K.I. (2000) Coniferopsida. In: Jonsell B. (ed.), Flora Nordica, vol. 1. The Bergius Foundation, Stockholm: 91-115.
De Koning J., Van den Broek J.W., Van de Laar H.J. & Fortgens G. (2000) Nederlandse dendrologie (13e druk). H. Veenman & zonen, Ede: 585 p.
Farjon A. (1990) Pinaceae: drawings and descriptions of the genera Abies, Cedrus, Pseudolarix, Keteleeria, Nothotsuga, Tsuga, Cathaya, Pseudotsuga, Larix and Picea. Regnum Vegetabile 121. Königstein, Koeltz Scientific Publications: 330 p.
Sell P.D. (1998) Conifers. In: Rich T.C.G. & Jermy A.C. (eds.), Plant crib: 35-40. BSBI, London.
Thieret J.W. (1993) Pinaceae. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 2. Oxford University Press, New York-Oxford: 352-398.