Seed anatomy: monocots, dicots and gymnosperms
Every seed is a plant embryo with a food supply and a protective coat. How those parts are arranged, and how many seed leaves the embryo has, explains how a seedling emerges and why some crops are fussy about depth.
Parts of a seed
The seed coat protects the embryo. Inside are the embryo (a tiny root, called the radicle, and a shoot) and a food store: either endosperm or the seed leaves (cotyledons) themselves. Water softens the coat, the radicle emerges first and the shoot follows.
Dicots
Dicot seeds have two seed leaves. Beans, peas, tomatoes, sunflowers, lettuce and most garden flowers are dicots. In a bean the two halves hold the food store; when it germinates the stem arches up and pulls the seed leaves into the light. In a pea the seed leaves stay underground. That is why bean seed that is sown too deep or crusted over struggles to emerge.
Monocots
Monocot seeds have one seed leaf and a separate starchy endosperm. Grasses, corn, onions, leeks, lilies, tulips and daffodils are monocots. The shoot emerges as a single pointed blade protected by a sheath, and leaves have parallel veins.
Monocot or dicot: quick test
One cotyledon, parallel leaf veins and scattered stem bundles suggest a monocot. Two cotyledons, net-veined leaves and a ring of stem bundles suggest a dicot.
Gymnosperms
Gymnosperm means naked seed: the seeds are not enclosed in a fruit. Conifers (pine, spruce, fir), ginkgo and cycads are gymnosperms. Seeds sit on the scales of cones and are often winged for wind dispersal. They have a food store from the female gametophyte and may have several seed leaves.
Conifer seed is often dormant and benefits from a cold-moist chill before sowing, and seedlings are slow. For fruit and fruit-tree seed see the fruit seeds guide.