The Most Primitive of the Dicot Plants and the Lily

Differences Between Monocots and Dicots

• The two groups have basic structural differences. Dicots have netted leaf veins, vascular bundles or the fluid-conducting tissues of the plant arranged in a ring inside the stem, floral parts in groups of four or five, herbaceous or woody growth, and taproots. Monocots have parallel leaf veins, scattered vascular bundles, floral parts in groups of three, mostly herbaceous growth and no taproot. A single-flowered California wild rose (Rosa californica), with five petals and woody growth, is an example of a dicot. An Easter lily (Lilium longiflorum), with six petals and herbaceous growth, is an example of a monocot. Easter lily grows in U.S. Department of Agriculture plant hardiness zones 4 through 9, and California rose in USDA zones 5 through 10.

Primitive Dicot Characteristics

• The subclass Magnoliidae -- containing the water lily family, the buttercup family and the magnolia family -- are generally considered the most primitive dicots. They share the characteristics of large flowers composed of petal-like structures that are both petals and sepals that look like petals, a cone-like central receptacle that bears the female carpels, surrounded by spirally arranged male flower parts called stamens. More technical, difficult-to-observe characteristics are having two-celled pollen grains rather than three-celled pollen; abundant endosperm, which is the food-providing part of the seed; and a comparatively small embryo within the seed.

The Most Primitive Dicots

• Water lilies possess a puzzling blend of both monocot and dicot characteristics, so they are thought to be among the most primitive dicots, perhaps linking to common ancestors. They have dicot netted leaf veining but a vascular bundle arrangement that resembles that of monocots. They have similar pollen structure to lilies and in the embryo, what appears to be a single cotyledon. Water lily flowers (Nymphaea spp.) are also primitive because they show the derivation of different flower parts from a similar basic structure. Flowers gradate from outermost sepal-like, green structures that morph into petal-like structures and then into stamen-like structures that are followed by true stamens. Recently, a New Caledonian rain forest shrub, Amborella trichopoda, was proposed as the most primitive living angiosperm.

Lily Plant Characteristics

• Lilies, although they share their common name with water lilies, are a classic example of a true monocot. The seed has a single, spear-like seed leaf. The seed root doesn't turn into a taproot, but disappears and is replaced by fibrous roots coming from a bulb that consists of scale leaves. The growth is herbaceous, and the flower has six petals, three of which are sepals that look like petals. Six stamens surround a central three-part ovary, which produces two rows of large flat seeds in each ovary part.