when you look at a leaf, how do you know if its monocot or dicot?

Answer 1

The traditionally listed differences between monocotyledons and dicotyledons are as follows. This is a broad sketch only, not invariably applicable, as there are a number of exceptions. The differences indicated are more true for monocots versus eudicots, as per the APG II system:

Flowers: In monocots, flowers are trimerous (number of flower parts in a whorl in threes) while in dicots the flowers are tetramerous or pentamerous (flower parts are in fours or fives).

Pollen: In monocots, pollen has one furrow or pore while dicots have three.

Seeds: In monocots, the embryo has one cotyledon while the embryo of the dicot has two.

Stems: In monocots, vascular bundles in the stem are scattered, in dicots arranged in a ring.

Roots: In monocots, roots are adventitious, while in dicots they develop from the radicle.


slice of onion, showing parallel veinsLeaves: In monocots, the major leaf veins are parallel, while in dicots they are reticulate.

However, these differences are not hard and fast: some monocots have characteristics more typical of dicots, and vice-versa. This is in part because "dicots" are a paraphyletic group with respect to monocots, and some dicots may be more closely related to monocots than to other dicots. In particular, several early-branching lineages of "dicots" share "monocot" characteristics, suggesting that these are not defining characters of monocots. When monocots are compared to eudicots, the differences are more concrete.