Class I. DICOTYLEDONOUS or EXOGENOUS PLANTS.
Stems increasing in diameter by the annual addition of a layer of wood inside the bark. Leaves netted-veined. Embryowith a pair of opposite cotyledons.
Sub-Class I. Angiospermse. Pistil, a closed ovary containing the ovules and developing into the fruit.
Division III. ApetalSB. Corolla 0. Stamens inserted on the petaloid calyx, or hypogynous.
51. Cupuliferse. Flowers monoecious or rarely perfect. Stamens 2 to 4 or indefinite. Ovary inferior, after anthesisimperfectly 2 to 3 or rarely 4 to 6-celled. Ovule solitary, or in pairs, ascending or descending, anatropous. Fruita nut usually more or less inclosed in bracts free or united into a woody involucre. Leaves alternate, stipulate.
52. Betulacese. Flowers monoecious. Stamens 2 to 4. Ovary inferior, 2-celled. Ovule solitary, suspended,anatropous. Fruit a nut covered by the deciduous or persistent scales of a strobile. Leaves alternate, stipulate.
53. Myricaceae. Flowers monoecious or dioecious. Stamens usually 4 to 6. Ovary inferior, 1-celled. Ovule soli-tary, erect, orthotropous. Fruit drupaceous, often covered with a waxy exudation. Leaves resinous-punctate, alternate,rarely stipulate.
54. Salicacese. Flowers monoecious. Perianth 0. Stamens 2 or many. Ovary 1-celled. Ovules numerous,ascending, anatropous. Fruit a 2 to 4-valved capsule. Leaves alternate, stipulate.