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Key to the Gymnosperms of Tennessee

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Key to the Gymnosperms

 * Pinus: Leaves needle-like in clusters of two to five with basal sheaths
 * 1: Leaves linear, scale-like, or awl-shaped, but not with a basal sheath.

1

 * 2: Leaves opposite, scale-like, or awl-shaped. Usually lass than 3.5 millimeters long
 * 3: Leaves alternate, linear, and over 3.5 millimeters long.

2

 * Thuja occidentalis: Cones woody, seeds winged, and twigs flattened
 * Juniperus virginiana: Cones berry-like, seeds wingless, and twigs 4-angled.

3

 * Taxodium distichum: Leaves and branchlets deciduous, unopened cones spherical, scales with supporting stalks.
 * 4: Leaves and branchlets evergreen, unopened cones longer than wide, scales flattened and without a stalk or scales absent.

4

 * Picea rubens: Leaves four-angled in cross-section.
 * 5: Leaves flat

5

 * Taxus canadensis: Leaves abruptly tapered at the tip. Single seeds enclosed in fleshy reddish aril.
 * 6

6

 * Tsuga: Cones hanging and less than 4 centimeters long. Leaves with short petiole-like bases.
 * Abies fraseri: Cones erect and less than 4 centimeters long. Leaves sessile.

Pinus

 * Pinus strobus: Leaves five per bundle. Scales of seed cones lack a prickle at the tip.
 * PIN1: Leaves two to four per bundle. Seed cones with prickles at the tip.

PIN1

 * Pinus taeda: Leaves over 13 centimeters long
 * PIN2: Leaves less than 13 centimeters long

PIN2

 * PIN3: Leaves two per bundle or rarely three per bundle
 * PIN4: Leaves three per bundle or rarely two or four per bundle

PIN3

 * Pinus virginiana: Seed cones asymmetric with stout, curved prickles
 * PIN5: Seed cones symmetric with fine, straight prickles.

PIN4

 * Pinus echinata: Leaves two or three per bundle. Needles flexible and straight to slightly twisted. Seed cones are short stalked.
 * Pinus rigida: Leaves three or four per bundle. Needles rigid and straight. Seed cones are subsessile.

PIN5

 * Pinus virginiana: Leaves strongly twisted and three to eight centimeters long.
 * Pinus echinata: Leaves straight or slightly twisted and seven to thirteen centimeters long.

Tsuga

 * Tsuga canadensis: Leaves less than 1.5 centimeters long and mostly arranged into one plane. Leaf margins are slightly serrulate and seed cones are less than two centimeters long.
 * Tsuga caroliniana: Leaves are less than 1.5 centimeters long and spirally arranged. Leaf margins are entire and seed cones are over two centimeters long.