5. Picea A. Dietrich, Fl. Berlin. 2: 794. 1824.
Spruce, épinette [Latin picis, pitch, name of a pitchy pine]
Ronald J. Taylor
Trees evergreen; crown broadly conic to spirelike; leading shoot erect. Bark gray to reddish brown, thin and scaly (with thin plates), sometimes with resin blisters (especially in Picea engelmannii and P . glauca ), becoming relatively thick and furrowed with age. Branches whorled; short (spur) shoots absent; twigs roughened by persistent leaf bases. Buds ovoid, apex rounded to acute, sometimes resinous. Leaves borne singly, spreading in all directions from twigs, persisting to 10 years, mostly 4-angled and square in cross section (to triangular or ± flattened), mostly rigid, sessile on peglike base; base decurrent, persistent after leaves shed, sheath absent; apex usually sharp-pointed, sometimes bluntly acute; resin canals 1--2. Cones borne on year-old twigs. Pollen cones grouped, axillary, oblong, yellow to purple. Seed cones maturing in 1 season, usually shed at maturity (persisting for several years in Picea mariana ), borne mostly on upper branches, pendent, ovoid to cylindric, sessile or terminal on leafy branchlets and thus appearing ± stalked; scales persistent, elliptic to fan-shaped, thin, lacking apophysis and umbo; bracts included. Seeds winged; cotyledons 5--l5. x =12.
Species ca. 35 (8 in the flora with 7 native and 1 naturalized): north temperate regions, North America, Mexico, Eurasia.
SELECTED REFERENCES
Roche, L. 1969. A genecological study of the genus Picea and seedlings grown in a nursery. New Phytol. 68: 505--554. Taylor, R.J. and T.F. Patterson. 1980. Biosystematics of Mexican spruce species and populations. Taxon 29: 421--469. Wright, J.W. 1955. Species crossability in spruce in relation to distribution and taxonomy. Forest Sci. 1: 319--349.
