Monocotyledons and Dicotyledons

1. Intro.

John Ray, near the end of the 17th century, was the first to establish a system of

classification that defined monocotyledons (one cotyledon or first seed leaf) and

dicotyledons (2 cotyledons or seed leaves)

Gymnosperms produce 3 - 9 grass like seed leaves.

2. Monocots:

Monocots have an embryo with one cotyledon or seed leaf.

Growth form is mostly herbaceous; a few are arborescent or tree like, such as bamboos

palms, and yuccas. These do not have secondary growth; a palm trunk is anatomically

a stack of leaf bases. About 10 % of the monocots appear woody.

Root system usually fibrous or a cluster of fleshy roots.

More of the plant body tends to be underground, as in bulbs.

Leaves are usually parallel veined, often with a sheathing leaf base; the petiole or leaf

stalk is seldom developed.

Vascular system consists of numerous scattered bundles, without definite arrangement.

Flowers usually have their parts in threes or multiples of 3 (3-merous).

Pollen is basically monocolpate, having one furrow or pore.

3. Dicots:

Dicots have an embryo with two cotyledona or seed leaves.

Growth form is either herbaceous or woody, with about 50 % of the plants being woody.

Root system often has a primary root that becomes a strong taproot, with smaller

secondary roots.

More or the plant body tends to be above ground.

Leaves are usually net veined, seldom sheathing at the leaf base; with the petiole

commonly developed.

Vascular system usually consists of a definite number of bundles in a ring, with a

cambium and secondary growth in diameter of the stem.

Flowers usually have their parts in fours or fives (4- or 5 -merous).

Pollen is basically tricolpate, having three furrows or pores.