Chapter 2 Leaves 1-nerved, needle-shaped, linear or scale-like, persistent (deciduous in Larix and Taxodium). Gymnosperm .

1. Leaves Persistent.

a Leaves fascicled, needle-shaped, in 1-5-leafed clusters enclosed at base in a membranaceous sheath.

Pinus (p. 2).

aa Leaves scattered, usually linear.

b Leaves linear, often obtuse or emarginate.

Base of the leaves persistent on the branches.

Leaves sessile, 4-sided, or flattened and stomatiferous above.

Picea (p. 34).

Leaves stalked, flattened and stomatiferous below, or angular, often appearing 2-ranked.

Tsuga (p. 42).

Base of the leaves not persistent on the branches; leaves often appearing 2-ranked.

Leaves stalked, flattened, stomatiferous below; winter-buds pointed, not resinous.

Pseudotsuga (p. 47).

Leaves sessile, flattened and often grooved on the upper side, or quadrangular, rarely stomatiferous above, on upper fertile branches often crowded; winter-buds obtuse, resinous (except in No. 9).

Abies (p. 50).

bb Leaves linear-lanceolate, rigid, acuminate, spirally disposed, appearing 2-ranked by a twist in the petiole.

Leaves abruptly contracted at base, long-pointed, with pale bands of stomata on the lower surface on each side of the midveins; fruit drupe-like.

Torreya (p. 91).

Leaves gradually narrowed at base, short-pointed, paler, and without distinct bands of stomata on the lower surface; fruit berry-like.

Taxus (p. 93).

bbb Leaves ovate-lanceolate and scale-like, spreading in 2 ranks or linear on the same tree, acute, compressed, keeled on the back and closely appressed or spreading at apex.

Sequoia (p. 61).

aaa Leaves opposite or whorled, usually scale-like.

Internodes distinctly longer than broad; branchlets flattened, of nearly equal color on both sides; leaves eglandular.

Libocedrus (p. 65).

Internodes about as long as broad, often pale below, usually glandular.

Branchlets flattened.

Branchlets in one plane, much flattened, 1/12′-?′ broad.

Thuya (p. 67).

Branchlets slightly flattened, 1/24′-1/16′ broad.

Cham?cyparis (p. 75).

Branchlets terete or 4-angled.

Branchlets more or less in one plane; fruit a cone.

Cupressus (p. 69).

Branchlets not in one plane; fruit a berry (leaves needle-shaped, in whorls of 3 in No. 1).

Juniperus (p. 78).

2. Leaves Deciduous.

Leaves in many-leafed clusters on short lateral spurs.

Larix (p. 31).

Leaves spreading in 2 ranks.

Taxodium (p. 63).