This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Embryo containing 2 or more (rarely 1) cotyledons, opposite or in a whorl. Leaves net-veined. Stem perennial, with pith, wood, and bark; with medullary rays, and increased by rings of wood on the outside yearly. Perianth of 4 or 5 or 2 divisions.
Perianth of 2 whorls, calyx and corolla; petals distinct as a rule.