Describing Flowering Plants and Plant Families: Quick Revision

A brief note on Describing Flowering Plants and Plant Families. Read it before a test. Try each question at the end before you open its answer.

The description

• Eight steps, in order: habit, root, stem, leaf, inflorescence, flower, fruit and seed, floral diagram and formula.
• Habit, root, stem and leaf give the vegetative characters. Inflorescence, flower, fruit and seed give the floral characters.
• The flower is described whorl by whorl: calyx, corolla, androecium, gynoecium.

The diagram and the formula

• A floral diagram shows the number of parts, their arrangement and how they are related.
• The dot at the top is the mother axis. The bract is an arc on the opposite side.
• Whorls run from the outside to the centre: calyx, corolla, androecium, gynoecium.
• The formula order: Br, symmetry, sex, K, C or P, A, G.
• A number gives how many parts. Brackets show fusion. A plus joins two groups.
• A line under G is a superior ovary. A line over G is an inferior ovary.
• A circled plus is a radial flower. A percent sign is a flower with one plane of symmetry.

The three families

• Fabaceae (pea): zygomorphic, papilionaceous corolla (standard, wings, keel), stamens nine and one, one carpel, a legume, root nodules.
• Solanaceae (potato): radial, joined sepals and petals, epipetalous stamens, two joined carpels, a berry or a capsule.
• Liliaceae (lily): a monocot, six tepals, epiphyllous stamens, three joined carpels, a capsule, bulbs and parallel veins.

A worked example

A flower has six free tepals in two rings of three, six stamens in two rings of three and three joined carpels. Name the family.

1. Six tepals in two rings mean the sepals and petals look alike.
2. Three joined carpels and a bulb fit a monocot.
3. Family: Liliaceae.

Practice with new numbers

A program to try

The program prints the formula of each family and adds the numbers in it.

Mistakes to avoid

• Writing K(5) for free sepals. Brackets mean fused.
• Mixing up superior and inferior. A line under G is superior.
• Calling the potato tuber a root. It is a swollen stem.
• Treating Liliaceae as a dicot. It is a monocot.

Check yourself

1. What does the dot in a floral diagram stand for?

2. Name the parts of a papilionaceous corolla.

3. What is the difference between epipetalous and epiphyllous stamens?

4. Which family has a bulb and parallel veins?