Flower Botany Basics: Angiosperms, Gymnosperms, and Flower Structure

Angiosperms are flowering plants with seeds enclosed in fruits. Their seeds have one or two cotyledons (seed leaves). Most garden plants are dicotyledons (two seed leaves)—maples, cabbages, roses. Monocotyledons (one cotyledon) include lilies, irises, palms, grasses (wheat, oats, rice). Gymnosperms (conifers, cycads) lack flowers and bear naked seeds with many cotyledons.

To botanists, a flower is a reproductive unit. Most are perfect (both sexes in one blossom). Some have separate male/female flowers on the same plant (corn, walnut, squash) or different plants (asparagus, holly, willow). Complete flowers have reproductive parts plus petals and sepals.

Floral Parts (in order)

• Receptacle: Attachment point of floral parts to stem tip; often enlarged.
• Sepals (calyx): Outer ring; usually green, sometimes colorful (fuchsia, iris).
• Petals (corolla): Next ring; showy part. Separate (camellia, rose) or fused into tubes/bells (rhododendron, petunia). Perianth = calyx + corolla.
• Stamens: Male parts. Filament (stalk) + anther (pollen sacs, usually yellow). Pollen = male gametes.
• Pistils: Female parts. Ovary + style (stalk) + stigma (pollen receiver). Ovules in ovary become seeds after fertilization.