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.
Order 78. Hydrocharidaceae. - Aquatic plants, floating or submerged; flowers regular, I-sexual; perianth 6-partite, in 2 series, inner petaloid; stamens 3 or more, epigynous; ovary inferior; 1- or 3 6-locular; styles free; fruit a berry.
Order 79. Orchidaceae. - Herbaceous plants; roots tuberous; flowers in spikes, 2-sexual, irregular; sepals 3, reversed; petals 3, 2 above, 1 below, spurred as a rule; stamens 1 or 2, adnate to style; ovary I-locular; ovules many, placentae 3, parietal; fruit a capsule; seeds numerous, minute.