About angiosperms (flowering plants)
Angiosperms are the flowering plants: only they have a true flower (perianth, stamens, pistil). The ovule lies inside the ovary, enclosed by its wall; after fertilization the ovule becomes a seed and the ovary a fruit, so the seed in the fruit is protected from cold, drought and pests. Another key feature is double fertilization: one sperm fuses with the egg cell, the second with the central cell. Their internal structure is also advanced: conducting vessels are made of long, lignified dead cells. The textbook gives over 250 000 species; today more than 300 000 are known, so they are by far the largest plant group. Dicots have 2 cotyledons in the embryo, keep the main root, have pinnate or palmate leaf veins, a stem with cambium (it thickens) and flower parts in 4s or 5s. Monocots have 1 cotyledon, a fibrous root system (adventitious roots), parallel or arc-shaped veins, a stem without cambium and flower parts in 3s.
| Feature | Dicots | Monocots |
|---|---|---|
| Cotyledons | 2 | 1 |
| Root | main root persists | fibrous |
| Leaf veins | pinnate or palmate | parallel or arcuate |
| Stem | has cambium, thickens | no cambium |
| Flower parts | in fours or fives | in threes |
Comparison: compare a bean seedling and a wheat seedling (or herbarium sheets): number of cotyledons, root, leaf veins. Safety: do not put seeds in your mouth (some may be treated with chemicals); wash hands; keep pots away from small children.