Topic 1.3 · Supplement
Monocotyledons and Dicotyledons
Flowering plants split into two groups, commonly shortened to monocots and dicots, and the names themselves tell you what to look for: mono means one, di means two, and a cotyledon is a seed leaf that forms part of the embryo inside a seed.
| Feature | Monocotyledons | Dicotyledons |
|---|---|---|
| Cotyledons | One | Two |
| Leaf veins | Usually parallel | Usually branching or net-like |
| Flower parts | Usually in multiples of 3 | Usually in multiples of 4 or 5 |
| Root system | Usually fibrous | Often a main tap root with side roots |
You don’t always need to open a seed to classify a flowering plant — the visible features above are usually enough on their own. A plant with parallel leaf veins and flower parts in multiples of three is likely to be a monocotyledon. A plant with branching leaf veins and flower parts in multiples of four or five is likely to be a dicotyledon. That’s the basis of the common monocot-versus-dicot comparison question, and as with every classification decision in this chapter, several matching features together give you stronger evidence than relying on just one.
This is the final layer of classification within the flowering plants group — every monocot and dicot has already passed the flowers-and-seeds test that separates flowering plants from ferns before this finer distinction even applies.