Dicotyledons with Incomplete Flowers — Betulcicece. 
107 
USES, &c.—The bark of Birch usually separates in papery or coriaceous laminae from the trunk ; in Paper 
Birch (Betula papyracea) of North America it is impermeable to water, and serves for the construction of light 
canoes and miscellaneous domestic and ornamental articles. The oil abounding in the bark of Common Birch is 
extracted for use in dressing Russia leather. The ascending sap in spring is more or less saccharine, and is collected 
from the cut extremities as an antiscorbutic beverage and for the preparation of Birch-wine. The wood of Birch is 
not very durable, though compact and easily worked. It is used in turnery. »That of Alder is used in submerged 
constructions. Charcoal prepared from the Alder is employed in the manufacture of gunpowder. 
Natural Order 
SALT CAGE A. Tab. 86. 
Diagnosis. —Trees or shrubs with alternate simple leaves. Flowers amen¬ 
taceous, unisexual, dioecious, achlamydeous or with a rudimentary perianth. 
Ovary 1-celled, with several or numerous ovules on 2 parietal placentas. 
Distribution.— A Natural Order consisting of two genera, of which one (Willow) includes about 
150 species widely distributed over the Globe, but by far most numerous in cool or Arctic climates. 
Number of British Genera, 2 ; Species, 32. 
Flowers destitute of a perianth in Willow ( Salix); with an oblique rudimentary perianth in Poplar (. Populus ). 
Stamens usually 2, 3 or 5 in Willow, 8-20-30 in Poplar. 
Fruit a small 2-valved capsule. 
Seeds minute, exalbuminous, with a basal tuft of silky hairs. 
USES, &c.—The slender, pliable, annual shoots of several species of Willow (osiers) are used in basket-making. 
The light wood of the larger species affords a valuable charcoal. The bark of a few species, both of Willow and 
Poplar, has been employed medicinally. 
