Who are the spore plants?
Some plants never make flowers or seeds. They make spores instead. A spore is a very tiny cell with a hard coat. It is so light that wind can carry it far.
The main spore plants are:
- Mosses: short, soft green cushions on walls, trees and wet soil.
- Club mosses (plauns): small plants with leaves like tiny scales along a creeping stem.
- Horsetails: stems with rings, like a green bottle brush.
- Ferns: large feathery leaves called fronds.
Moss is the simplest. It has no true root. It has tiny thread-like holders called rhizoids. Ferns have real roots, a stem and leaves with tubes inside to carry water.
Life cycle of a moss
The green, leafy cushion you see is the moss plant that makes egg and sperm. Follow the loop:
- The green moss plant makes sperm and egg at its top.
- When it rains, sperm swim through the water film to an egg.
- The joined egg grows into a thin stalk with a capsule on top. The stalk stays fixed on the green moss and takes food from it.
- The capsule dries and opens. Thousands of spores fly out.
- A spore falls on damp ground and first grows into a green thread. Buds on the thread grow into new moss plants.
Life cycle of a fern
In a fern, the big plant with the feathery fronds is the one that makes spores.
- On the back of mature fronds you see brown dots (sori). Each dot is a group of tiny spore cases.
- The cases pop open. Spores fall to damp soil.
- A spore grows into a tiny, flat, heart-shaped green plant called the prothallus. It is about as small as a fingernail or smaller, and it lies flat on the soil.
- The heart-shaped plant makes egg and sperm on its underside.
- When the soil is wet, sperm swim to the egg. The joined cell grows into a young fern, and the heart-shaped plant slowly dies.
Horsetails and club mosses follow the same pattern: spores, a tiny plant, swimming sperm, a new plant.
Why do spore plants live in damp places?
The sperm must swim. They can only swim in a thin layer of water, like rain or dew. So the plant needs a wet place at least once in its life cycle. That is why moss and ferns love shade, rain forests, river banks and wet walls.
Seed plants are different. Their pollen can travel by wind or insects, so they can live in dry places too.
Try it: grow your own moss and look at a fern
1. In the monsoon, look for a green patch on a wall. Touch it. Is it soft? Does it have flowers? Look closely for tiny stalks with capsules.
2. Find a fern leaf. Turn it over. Draw the brown dots.
3. In the 3D above, go to the last step. Slide the water to zero and press Run the cycle. Predict where the red ball will stop before you press it.
Key formulas and definitions
- Spore plant = no flower + no seed + makes spores
- Moss cycle: green plant โ egg + sperm โ capsule โ spores โ green thread โ moss
- Fern cycle: fern โ spores in sori โ heart-shaped plant (prothallus) โ egg + sperm โ new fern
- Sperm need a film of water to swim to the egg
Worked examples
1. A student sees a brown dot pattern under a leaf of a plant with no flowers. What is the plant likely to be, and what are the dots?
It is likely a fern. The brown dots are sori, groups of cases that hold spores.
2. Why can moss spread across a rainy-season wall but not across a sunny, dry rock all year?
Moss sperm need a water film to swim to the egg. The rainy-season wall stays wet, so the cycle can finish. A dry rock has no water film, so the sperm cannot reach the egg.
3. Write the correct order: new fern, spores, heart-shaped plant, sperm swim, fern with sori.
Fern with sori, spores, heart-shaped plant, sperm swim, new fern.
Common mistakes
- Saying ferns have seeds. They have spores, not seeds. A spore is one small cell; a seed has a baby plant and food stored inside.
- Thinking the brown dots under a fern leaf are insects or disease. They are normal spore cases.
- Mixing up the heart-shaped plant and the fern. The tiny heart-shaped plant comes from a spore and is not the big feathery fern.
- Forgetting water. Without a film of water, the sperm cannot swim and no new plant forms.