1. Algae are unicellular or multicellular, filamentous, colonial or mycelial.
2. Their body cannot be divided into roots, stems and leaves. That is, they are thallus shaped.
3. They are green, self-feeding and self-sustaining. i.e. contains photosynthetic pigments (exception – Polytoma).
4. Algal plastids contain one or more pyrenoids. It stores sugar.
5. Algae are mainly gametophytic plants.
6. Their cell walls are composed of cellulose and pectin (exception – Euglenophyta).
7. Their stored food is sugar (glycogen in cyanobacteria). May also contain alcohol, oil and fat
8. Cells have a well-organized nucleus.
9. Their chromatin bodies contain DNA, RNA and proteins.
10. Their genitalia are unicellular and not covered by a sterile sheath (exception – Chara).
11. Their sporangium is unicellular. Asexual reproduction occurs by unicellular spores.
12. They do not have transport canals or vascular bundles. That is, they are avascular.
13. Their cell division is amitosis, mitosis and meiosis.
14. Sexual reproduction is isogamous, anisogamous and eugamous in nature.
15. Sunlight is essential for their survival.
16. Multicellular embryos are never formed in their life cycle. Life cycle does not show clear phylogeny.
17. They are mostly aquatic. But can be terrestrial, semiaquatic, epiphytic and endophytic.
18. They can grow in frost, air and snow.