Protonema is formed from the rhizoids of some algae. New algae grow from these protonema. Like- Chara, Nitella etc.

White matter accumulates in the body of some algae and forms a star-shaped organ. They are called starch stars or amylum stars. Later new algae are born from the starch star. Like Chara, Botrydium etc.

In unfavorable environment, one or more cells of some protozoan algae swell to store large amounts of food and develop into resting spores covered by a thick wall. These cells are called akinites. Each actinomycete germinates into a new alga in a favorable environment. Such as Nostoc, Oscillatoria, Pithophora, Ulothrix, Gloeotrichea, Revularia etc.

Tuber or bulbil is produced by the accumulation of food above and below the rhizoid in some algae. These separate from the mother body and form new algae. Like- Chara, Cladophora, Botrydium etc.

In unfavorable environment hormogonium of algae is covered by thick wall to form hormocyst. Under favorable conditions, hormocysts germinate and give rise to new algae. Eg Nostoc, Oscillatoria etc.

Trichrome of blue-green algae breaks down to form hormogonia. The hormogonium is covered by a thick wall to form the hormocyst. New algae are produced from hormogonia in favorable conditions. Eg Nostoc, Oscillatoria etc.

In favorable environment, the algae grows in size by taking food and outgrowths form from the side of the body. A bud or bud is then produced from the subgrowth and the bud separates from the mother body to give rise to new algae. Eg- Protosiphon.

When filaments and colonies of multicellular algae are divided into two or more segments by injury or physical reasons, a new algae is formed from each segment. E.g. Ulothrix, Oedogonium, Spirogyra, Nostoc, Oscillatoria etc.

1. By fission: Unicellular algae grow in size by taking food and divide into two new algae by fission process. Like- Chlorella, Euglena, Navicula, Diatom, Protococcus, Gloeocapsa, Synechococcus etc.
2. Segment: When filaments and colonies of multicellular algae are divided into two or more segments by injury or physical reasons, a new algae is formed from each segment. E.g. Ulothrix, Oedogonium, Spirogyra, Nostoc, Oscillatoria etc.
3. Budding: In favorable environment, the algae grows in size by taking food and outgrowths form from the side of the body. A bud or bud is then produced from the subgrowth and the bud separates from the mother body to give rise to new algae. Eg- Protosiphon.
4. Hormogonia: Trichrome of blue-green algae breaks down to form hormogonia. The hormogonium is covered by a thick wall to form the hormocyst. New algae are produced from hormogonia in favorable conditions. Eg Nostoc, Oscillatoria etc.
5. Hormocysts: In unfavorable environment hormogonium of algae is covered by thick wall to form hormocyst. Under favorable conditions, hormocysts germinate and give rise to new algae. Eg Nostoc, Oscillatoria etc.
6. Tuber/Bulbil: Tuber or bulbil is produced by the accumulation of food above and below the rhizoid in some algae. These separate from the mother body and form new algae. Like- Chara, Cladophora, Botrydium etc.
7. Akinity: In unfavorable environment, one or more cells of some protozoan algae swell to store large amounts of food and develop into resting spores covered by a thick wall. These cells are called akinites. Each actinomycete germinates into a new alga in a favorable environment. Such as Nostoc, Oscillatoria, Pithophora, Ulothrix, Gloeotrichea, Revularia etc.
8. Star stach: White matter accumulates in the body of some algae and forms a star-shaped organ. They are called starch stars or amylum stars. Later new algae are born from the starch star. Like Chara, Botrydium etc.
9. Protonema: Protonema is formed from the rhizoids of some algae. New algae grow from these protonema. Like- Chara, Nitella etc.

Stirring ocean water in the tropics ignites fire and produces light. This is called bioluminescence. Pyrrophyta is caused by algae. They create red tides. Pyrrophyta algae contain luciferin. Luciferin is phosphorylated by ATP to form new molecules. The resulting material reacts with oxygen in the presence of the enzyme luciferase to emit light.