Classification of Algae By Fritsch (11 Classes of Algae)

In this article we will discuss about Classification of algae by F.E. Fritsch (1935-45):- 1.Chlorophyceae, 2.Xanthophyceae, 3.Chrysophyceae, 4.Bacillariophyceae, 5.Cryptophyceae, 6.Dinophyceae, 7.Chloromonadineae, 8.Euglenineae, 9.Phaeophyceae, 10.Rhodophyceae and 11.Myxophyceae

F.E Fritsch Classification is one of the best and accepted classifications in algology.
The classification of algae is published in his book titled “The Structure and Reproduction of Algae”.
He proposed classification of algae on the basis of reserve food material, flagellation, pigments, thallus structure and modes of reproduction
The scheme of classification of algae as proposed by him is as follows: Chlorophyceae, Xanthophyceae, Chrysophyceae, Bacillariophyceae, Cryptophyceae, Dinophyceae, Chloromonadineae, Euglenophyceae, Phaeophyceae, Rhodophyceae and Myxophyceae

Table of Contents

Fritsch Classification of Algae (11 Classes)

The scheme of classification of algae as proposed by him is as follows

Class 1 – Chlorophyceae (Green Algae)

Occurrence: Most forms are fresh water and a few are marine.
Pigments: Chlorophyll a, b, carotenoids (yellow pigments) and xanthophylls. They are green in colour due to dominance of chlorophyll a and b pigments.
Reserve food: Starch
Flagella: Motile cells have equal flagella (2-4)
Structure: Unicellular motile to heterotrichous filaments. Cell wall consists of cellulose. Pyrenoids are present.
Reproduction: Sexual reproduction ranges from isogamous to advanced oogamous type.
Chlorophyceae is divided into 9 orders.
E.g. Volvox, Chlorella, Ulothrix, Cladophora, Fritschiella, Oedogonium, Zygnema, Vaucheria and Chara

Class 2 – Xanthophyceae (Yellow Green Algae)

Occurrence: Most forms are fresh water but a few are marine.
Pigments: Chlorophyll a, e, β- carotene and xanthophylls. The members are yellow green in colour due to excess of xanthophylls.
Reserve food: Fat
Flagella: Motile cells have two unequal flagella.
Structure: Unicellular motile to simple filamentous. Cell wall rich in pectic compounds and Pyrenoids absent
Reproduction: Sexual reproduction is rare and if present always isogamous.
Xanthophyceae is divided into 4 orders.
E.g. Heterochloris, Chloramoeba, Myxochloris, Tribonema and Botrydium

Class 3 – Chrysophyceae

Occurrence: Mostly occur in fresh water but few are marine.
Pigments: Chlorophyll a, β-carotene and phycochrysin. The colour of the algae is golden brown or orange due to the excess presence of phycochrysin.
Reserve food: Oil and leucosine
Flagella: Have 1 flagellum. Sometimes 2 or 3 flagella (unequal)
Structure: Colonial forms unicellular motile to branched filamentous. Cells commonly contain one or two parietal chrmoatophores.
Reproduction: Sexual reproduction is rare as in case of Xanthophyceae and if present then it is isogamous.
Chrysophyceae is divided into 3 orders.
E.g. Chrysodendron, Chrysosphaera and Chrysoclonium

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Class 4 – Bacillariophyceae (Diatoms)

Occurrence: Found in fresh water, sea and terrestrial habitats.
Pigments: Chlorophyll a and c, β- carotene and xanthophylls. Dominant pigment is diatomin (yellow or golden brown in colour).
Reserve food: Oil, volutin and leucosine
Flagella: Have single flagellum
Structure: All the members are unicellular or colonial. Cell wall is divided into two halves, pectic, silicified and ornamented
Reproduction: Sexual reproduction is isogamy (Pennales) or oogamous (Centrales) and formation of auxospores. This auxospores help diatom to regain its original size.
Bacillariophyceae is divided into 2 orders.
E.g. Pinnularia, Cyclotella and Grammatophora

Class 5 – Cryptophyceae

Occurrence: They are fresh water and marine both
Pigments: Chlorophyll a, c and xanthophylls. Chromatophores show diverse pigmentation (brown, red, olive green, or sometimes bluish green) and except the phycobilins.
Reserve food: Starch
Flagella: Motile cells are biflagellate and are unequal in length.
Structure: Most advanced forms are coccoid. Each cell consists of two large chloroplasts. Chromatophores are usually parietal. A complex vacuolar system is present in the cell.
Reproduction: Sexual reproduction is rare and when present it is of isogamous type
Cryptophyceae is divided into 2 orders.
E.g. Chroomonas, Cryptomonas, Tetragonidium

Class 6 – Dinophyceae (Dinoflagellates)

Occurrence: Occur widely as sea water planktons. A few may be fresh water forms.
Pigments: Chlorophyll a, c, β- carotene, peridinin and chlorophyllin. The colour of the members is brown or dark yellow due to the presence of peridinin and chlorophyllin.
Reserve food: Starch and oil
Flagella: Motile cells are biflagellate.
Structure: They are unicellular motile to branched filamentous. Large nucleus and many discs like chromatophores are present.
Reproduction: Sexual reproduction is of isogamous type. it is rare and not very definite.
Dinophyceae is divided into 6 orders.
E.g. Dinoflagellate , Ceratium, Peridinium

Class 7 – Chloromonadineae

Occurrence: They are only fresh water forms.
Pigments: Chlorophyll a, b and xanthophylls. They are bright green in colour due to the presence of excess xanthophylls and cells have numerous discoid chromatophores.
Reserve food: Fat and oil
Flagella: The motile forms are with two almost equal flagella.
Structure: Unicellular algae and pyrenoids are lacking
Reproduction: Sexual reproduction is absent. Multiplication takes place by longitudinal division of cells.
Chloromonadineae is divided into 1 orders.
E.g. Vacuolaria, Trentonia

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Class 8 – Euglenophyceae

Occurrence: Members are fresh water forms.
Pigments: Chlorophyll a, b, β- carotene, neoxanthin, astaxanthin and diadinoxanthin. Chromatophores are pure green.
Reserve food: Paramylon and fats
Flagella: Flagella may be one or two arising from the base of canal like invagination at the front end.
Structure: Motile, have complex vacuolar system and a large and prominent nucleus. Each cell has several chromatophores.
Reproduction: Reproduction usually takes place by fission. Sexual reproduction is not substantially known. If present it is isogamous type.
Euglenophyceae is divided into 2 orders.
E.g. Euglena, Heteronema

Class 9 – Phaeophyceae (Brown Algae)

Occurrence: Mostly marine
Pigments: Chlorophyll a, c, β- carotene and fucoxanthin. The brown colour is due to excess fucoxanthin.
Reserve food: Laminarin and mannitol
Flagella: Motile cells are biflagellate with unequal length and attached laterally
Structure: These are the most complex algae and simple filamentous to bulky parenchymatous forms. Algin and fucoidin is present in cellulosic cell wall. Several plants attain giant size, external and internal differentiation.
Reproduction: It ranges isogamous to oogamous.
Phaeophyceae is divided into 9 orders.
E.g. Ectocarpus, Sargassum, Dictyota, Laminaria, Fucus

Class 10 – Rhodophyceae (Red Algae)

Occurrence: Few forms are fresh water and others are marine.
Pigments: chlorophyll a, d, α- and β-carotene, xanthophyll’s, r-phycoerythrin and r-phycocyanin give red color to these algae.
Reserve food: Floridean starch
Flagella: Motile cells are absent
Structure: Simple filamentous to complexity of structure. Plasmodesmata is present in the cells except Protoflorideae.
Reproduction: Sexual reproduction is advanced oogamous type. The male organ produces non motile gametes and female organ has a long receptive neck. After sexual reproduction special spores (carpospores) are produced
Rhodophyceae is divided into 7 orders.
E.g. Polysiphonia, Porphyra, Gelidium, Gracilaria

Class 11 – Myxophyceae or Cyanophyceae (Blue Green Algae)

Occurrence: Found in sea and fresh water
Pigments: chlorophyll a, α-carotene, β-carotene, c-phycocyanin and c-phycoerythrin.
Reserve food: Cyanophycean starch
Flagella: Motile cells are absent
Structure: Simple cell to filamentous, some of the filamentous forms show false or true branching, very rudimentary nucleus and no proper chromatophores. Most of the members are embedded in mucilaginous sheath.
Reproduction: Sexual reproduction is absent, Asexual reproduction by harmogonia or akinetes.
Myxophyceae is divided into 5 orders.
E.g. Gleocapsa, Dermocarpa, Oscillatoria, Nostoc

Class 12 – Nematophyceae (Fossil Algae)

Apart from these 11 classes, Nematophyceae, a fossil group with two genera, was also suggested by Fritsch.
True affinities of this class are unknown but their internal morphology is similar to Chlorophyceae.
Their spore tetrads are similar to Rhodophyceae.
E.g. Nematoplexus, Prototaxites