HEMLOCK (Tsuga spp

Description

Hemlock: Nine species of evergreen, mostly hardy, coniferous trees, belong to the genus Tsuga. They are medium to large in size.
and usually pyramid-shaped. Native to North America, Japan, Formosa, China, and the Himalayas, the species has horizontal branches, solitary monoecious flowers, and globose to ovoid or oblong cones with thin, persistent scales. The bark of T. canadensis is a valuable source of tannin. T. heterophylla is the largest North American species, being 70 m (230 ft.) or more in height.
Spruce: Picea glauca is a tall tree (15 to 45 m., or 49 to 148 ft. tall) resembling the balsam fir (Abies balsamea). White spruce has slender, pale, glaucous leaves and cylindrical cones with thin scales.
P canadensis is a lower tree of 8 to 12 m (26 to 39 ft.). It has short, thick, pale bluish-green leaves and short, ovoid, or subglobose cones persisting for several years.
Distillation of needles and twigs of the above plants, the only parts used, yields hemlock and spruce oils. No attempt is made to keep these species separate for oil production; hence, spruce oil and hemlock oil are used interchangeably in commercial practice. Hemlock (spruce) has a pleasant balsamic, fresh, pine-needle odor.
The essential oil is obtained by steam distillation of needles and twigs from the above-mentioned botanical sources. It is a paleyellow to light-yellow liquid with a pleasant, pine-needle odor. Its main constituents include bornyl acetate, bomeol, α-pinene, camphene, limonene, β-pinene, and myrcene.