Algae, mosses and lichens

Kingdom Plantae: many-celled, make their own food, with stiff cell walls of cellulose. They are the base of most food chains and give out oxygen. Plants are sorted into five classes. A memory hook, "The Brave Prince Grew Apples":

• Thallophyta;
• Bryophyta;
• Pteridophyta;
• Gymnosperms;
• Angiosperms.

Each step up is a little better suited to life on land.

Thallophyta (algae) are the simplest. Their body is a thallus: no roots, stems or leaves. It is so simple and small that it takes in gases, water and nutrients directly from the water around it. They live mostly in water or damp places, like the green slime (kaai) where water keeps flowing. Example: *Spirogyra*.

**Bryophyta (mosses and liverworts such as Marchantia) were a first step onto land**. You see them as green mats on damp rocks, walls and soil, especially in the monsoon. They have:

• root-like threads called rhizoids;
• simple stem-like and leaf-like parts;
• but no true roots, stems or leaves, and no pipes (vascular tissue) to carry water.

Bryophytes still need water to reproduce: their male cells swim to the female cells. That's why they are called the amphibians of the plant kingdom.

Lichens are the white-green patches on tree trunks and stones. Each is a partnership: an alga makes the food, and a fungus gives protection.

• Their colour changes with air pollution, so scientists use them to measure air quality (they are bioindicators). Village elders see them as a sign of clean air.
• Some, called *patthar ke phool*, are used as a spice, as medicine, or to dye wool and silk.
• Some are poisonous, so they must be identified carefully before use.