The Onion Seedling

From a distance an onion seedling comes up looking like a dicotyledon. But an onion is a monocotyledon; a single embryonic leaf emerging from its seed.

A day or two later, the illusion of a dicot gives way to the monocot as the tip emerges from the soil, a pronounced fold in its embryonic leaf. Other features of a monocot: roots are adventitious, flower parts come in threes, and veins are parallel. Lilies, bananas, ginger and grasses are monocots.