II. Leaves 1-nerved, needle-shaped, linear or scale-like, persistent (deciduous in Larix and Taxodium). Gymnospermæ.
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′—⅙′ broad.Thuya ([p. 67]). Branchlets slightly flattened, 1/24′—1/16′ broad.Chamæcyparis ([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]).
III. Leaves netted-veined, rarely scale-like or wanting. Dicotyledons.
A. LEAVES OPPOSITE. (B, see [p. xix]).
1. Leaves Simple. (2, see [p. xviii]).
Leaves persistent.