Algae range from one-celled microalgae like Chlorella, Prototheca, and Ochrophyta (diatoms) to multicellular forms, including the large seaweeds, of which the largest, the giant kelp (Macrocystis pyrifera, see below), may grow up to 50 m long. The most complex freshwater forms are the Charophyta, a division of green algae, which includes Spirogyra and Charales (stoneworts).

Cyanobacteria, popularly known as blue-green algae, mostly live in freshwater, producing energy through photosynthesis. Even though they are not really algae, they are included here due to their popular name. A few pictures of these organisms are shown at the bottom of the page.

Lichens are double organisms, consisting of a fungus and an alga or a cyanobacterium, living in a mutual symbiotic relationship. The alga or the cyanobacterium is attached to the mycelium of the fungus, which is again attached to the soil, or to stones or trees. Thus, the alga or cyanobacterium is protected from most enemies, and in return it provides the fungus with essential carbohydrates that the fungus cannot produce. The mycelium, however, is able to obtain certain nutrients from the soil or from the air, which benefit the alga or cyanobacterium.

Some species of marine algae form symbiotic relationships with other organisms than lichens or cyanobacteria, for instance corals or sea sponges.

 

Green algae (Chlorophyta and Streptophyta) are a huge and diverse group, containing between 9,000 and 12,000 species. The name Chlorophyta is derived from Ancient Greek chloros (‘green’) and phyton (‘plant’), Streptophyta from Ancient Greek strepto (‘twisted’) and again phyton, where strepto alludes to the morphology of the sperm of some members.

Stoneworts (Charophyceae) are a class of green algae, comprising about 400 species worldwide, most of which grow in freshwater, a few in brackish water. These organisms may grow to 1.2 m long and are strongly branched, with leaves in whorls. They produce energy via photosynthesis. They are often abundant in clear lakes and ponds, but disappear with growing eutrophication, suffocated by increased production of plant plankton.

The name stonewort stems from a layer of calcium carbonate, which over time may be encrusted on these plants.

Red algae (Rhodophyta) are one of the oldest groups of algae, containing over 7,000 species, the vast majority consisting of marine algae, including many notable seaweeds, whereas they are rare in freshwater habitats. The name is derived from Ancient Greek rhodon (‘rose’) and phyton (‘plant’), thus ‘rose-coloured plant’.

Brown algae (Phaeophyceae) constitute a huge group of large algae, comprising between 1,500 and 2,000 species, including many species in colder waters of the Northern Hemisphere. In daily speech, they are called kelp or seaweeds. Some members of the group are consumed by people, especially in the Far East.

Most of the yellow or yellow-green algae (Xanthophyceae), also known as mustard algae, are yellowish, but may sometimes be bright orange. They mainly live in fresh water, but some are found in the sea, others on land, where they may cling to various surfaces, usually in humid places. They vary from single-celled flagellates to simple colonies and filamentous forms. Supposedly, their nearest relatives are the brown algae.

 

 

It is restricted to the northern Atlantic Ocean, from Svalbard southwards to Portugal, in eastern Greenland and southwards to the north-eastern coasts of North America.

The name is derived from Ancient Greek askos (‘bag’ or ‘bladder’) and phyllon (‘leaf’), and from the Latin nodosus (‘knotted’), from nodus (‘joint’), referring to the air bladders on the fronds.

 

 

 

 

 

Attached to stones or rocks, the branched fronds of this plant may grow to 90 cm long and 2.5 cm wide. Along both sides of the prominent midrib are a number of almost globular air bladders.

Since 1811, this species has been a source of iodine, utilized to treat goitre, a swelling of the thyroid gland, caused by lack of iodine.

The generic name stems from Ancient Greek phukos, a term used for seaweeds. The specific name is derived from the Latin vesicula (‘small bladder’), and the suffix osus (‘full of’).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In Ireland, where this species is known as dúlamán, it was collected for food during famines. A local folk song, Dúlamán, describes a growing relationship between two people who collect the seaweed as a profession.

The generic name was given in honour of French botanist Auguste Pelvet (1821-1859). The specific name is derived from the Latin canaliculus (‘small channel’), and the suffix atus (‘having’).

 

 

 

 

 

 

 

The name is derived from the Latin lamina (a thin plate or layer) and the suffix arius (‘resembling’), referring to the large and flat fronds of many of these algae.

 

The name is derived from Ancient Greek makros (‘long’ or ‘large’) and kystis (‘bladder’ or ‘sac’), and the Latin pyrus (‘pear’) and fero (‘to carry’), alluding to its large size, and to the numerous pear-shaped bladders that keep it floating.

 

 

 

 

 

 

 

 

 

The generic name is derived from Ancient Greek Nereis (originally a sea god, but in Latin meaning a mermaid), and kystis (‘bladder’), thus ‘mermaid’s bladder’.

The specific name was applied in honour of German-Russian navigator, geographer, and Arctic explorer Friedrich Benjamin Graf von Lütke (1797-1882), in Russia known as Fyodor Petrovich Litke.

 

 

 

 

 

 

 

 

 

The generic name was given in honour of German-Estonian geologist and artist Alexander Philipov Postels (1801-1871).

 

 

 

 

 

 

The generic name was given in honour of German clergyman and botanist Johann Friedrich Trentepohl (1748-1806). The specific name is Latin, meaning ‘golden’.

 

 

 

 

 

 

 

 

The name Ulva can be traced back to a Celtic word for marsh plants, and it became a classical Latin term for sedges (Carex). Why Swedish naturalist Carl Linnaeus (1707-1778) applied the name to these sea plants is not known. – His life is described on the page People: Famous naturalists.

The specific name is derived from Armorica, the classical Latin name for the coastal region of Brittany. This word can be traced back to Celtic are-mori (‘by the sea’).

 

 

 

 

 

The specific name refers to the fronds.

 

 

 

 

 

 

 

The specific name is Latin, meaning ‘lettuce’, applied in 1753 by Linnaeus (see above) due to its striking resemblance to garden lettuce (Lactuca sativa).

 

 

 

 

 

 

 

 

 

 

 

Linnaeus is presented on the page People: Famous naturalists.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The gods appealed to the supreme god Vishnu for help, and he suggested that they should regain their power by drinking the miraculous amrita, the nectar of immortality, which they could obtain by churning the cosmic milk ocean, thus bringing the jar with amrita to the surface.

However, Vishnu advised the other gods to treat the asuras diplomatically by suggesting them to jointly churn the ocean. When the amrita was brought to the surface, Vishnu would ensure that the gods got hold of it.

The asuras readily agreed to participate in the churning. To perform this stupendous task, the gods and the asuras uprooted the mountain Mandara, placed it upside down in the ocean, and coiled the giant, many-headed naga (serpent) Vasuki around it. By pulling alternately at each end of Vasuki, the mountain would act as a gigantic churn, thus bringing the amrita to the surface.

The mountain, however, began sinking into the ocean floor, causing Vishnu to assume the shape of a giant, named Kurma, half man, half turtle. He then dove to the bottom of the sea, where he placed Mandara on his back, thus preventing the mountain from sinking.

Finally, the jar with amrita surfaced, whereupon a fierce battle between the gods and the asuras ensued, the latter grabbing the jar and running away with it.

Again, the gods appealed to Vishnu, who assumed the form of a new avatar, Mohini, a beautiful goddess, who seduced the asuras and managed to get hold of the jar of amrita, thus preventing evil from becoming eternal, and preserving the good.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Elsewhere, however, this tree has been planted extensively, especially in Australia, New Zealand, Spain, Argentina, Chile, Uruguay, Kenya, South Africa, and the island of Tristan da Cunha.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Lichens can grow on almost any surface, and they occur from sea level to high mountains. In the Himalaya, they have been found at elevations above 6000 m. They are very common on stones and tree bark, or they may grow on plants, fungi, or even other lichens. However, the vast majority are merely epiphytes, only a few being parasitic.

 

 

Cup lichens are widely distributed in the Northern Hemisphere, found on the ground or on rocks. The thallus varies in shape from simple and pointed to cup-shaped and can be yellow, gray, or brown in colour.

Reindeer lichens cover vast areas in the northern tundra and taiga areas, and although they grow very slowly (3-5 mm per year), they constitute a very important food item for reindeer or caribou (Rangifer tarandus), moose or elk (Alces alces), and musk ox (Ovibos moschatus).

Cup lichens contain a gummy or starchy material, which, boiled with milk or syrup, has been used as a remedy for whooping cough and chest ailments.

In Scandinavia, reindeer lichens have been used in the manufacture of alcohol. In Denmark, in the 1700s, these lichens were harvested in great quantities and, mixed with heather (Calluna vulgaris) used as winter fodder for cattle and sheep.

The generic name is derived from Ancient Greek klados (‘branch’), thus ‘branched’ – an apt name for many members of the genus.

 

 

 

 

It is known by several popular names, including gritty British soldiers, Bengal matches, and Devil’s matchsticks, all alluding to the red sporangia, situated at the end of a short stalk. In the old days, uniforms of British soldiers were bright red. Bengal matches were mostly produced in India, hence the name. They were larger than ordinary matches and burned with a larger, brigtly coloured flame, hence the name Devil’s matchsticks.

The specific name honours German botanist and lichenologist Heinrich Gustav Flörke (1764-1835), who initially studied theology, mathematics, and medicine, but in 1816 he was appointed professor of natural history at the University of Rostock, where he remained for the rest of his life. He specialized in lichens, primarily studying the genus Cladonia. For a number of years, he was an editor of Oekonomische Encyklopädie (‘Economic Encyclopedia’).

 

 

 

 

 

The specific name is Latin, meaning ‘star-like’, referring to the radiating tips of the branches.

 

 

 

 

 

 

The generic name is derived from the Latin letalis (‘deadly’), referring to the high toxicity of vulpinic acid, a chemical produced by the lichen. In the old days, the common wolf lichen (L. vulpina) was utilized by the Norwegians to kill wolves and foxes. Its foliage was mixed with crushed glass, and then stuffed into a carcass on frozen ground. The specific name refers to foxes, in Latin Vulpes.

Common wolf lichen and brown-eyed wolf lichen (L. columbiana) are both found in California, where many native peoples formerly utilized them for a variety of purposes. Their foliage was used to produce arrow poison. Klamath people would soak porcupine quills in an extract of the plants, which dyed them yellow. They were then woven into baskets to make patterns. The Okanagan-Colville tribe used these lichens medicinally, internally for stomach problems, externally for wounds.

 

 

 

 

 

 

 

 

 

The medicinal usage of old-man’s-beard lichens is described on the page Plants: Plants in folklore and poetry.

The generic name derives from Arabic ušna (‘moss’). In former days, botanists didn’t distinguish between mosses and lichens.

 

 

 

 

 

 

 

 

 

The specific name is Latin, meaning ‘very long’.

 

 

 

 

 

 

 

 

 

The first part of the generic name is derived from Ancient Greek xanthos (‘yellow’), referring to the yellowish upper surface of these lichens. The last part is Latin, meaning ‘spotted’. It is not clear what it refers to.

 

The specific name is derived from the Latin convolutus (‘to roll up’ or ‘to entwine’), referring to the thallus, which in dry periods curls into tight, twisted scrolls, which unroll when conditions again become humid.

 

 

 

 

 

 

Previously, these organisms constituted a separate family, Lobariaceae, but have since been moved to Peltigeraceae.

The generic name is Latin, meaning ‘lobed’, ultimately derived from Ancient Greek lobos (‘a lobe of the liver’), alluding to the lobed thallus. The common names likewise refer to the surface of the thallus, which resembles that of a lung.

 

 

 

 

 

The specific name is derived from the Latin pulmo (‘lung’), like the generic and common names alluding to the surface of the thallus, which resembles that of a lung.

 

 

 

 

 

 

 

The name is derived from Ancient Greek telos (‘end’) and schizein (‘to split’), alluding to the finely divided, split ends of the thallus branches, characteristic of the type genus Teloschistes.

 

The generic name is derived from Ancient Greek xanthos (‘yellow’) and the suffix oria (‘close to’), referring to the orange-yellow colour of these lichens.

 

 

 

 

 

The specific name is Latin, meaning ‘golden’, of course alluding to its colour.

 

 

 

 

 

 

 

 

 

The specific name, from the Latin paries (‘wall’), was applied by Swedish naturalist Carolus Linnaeus (1707-1778) in 1753. His life is described on the page People: Famous naturalists.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Proliferate reproduction of these ‘algae’ often takes place late in the summer. They sometimes occur in huge masses, dying ponds and lakes a characteristic bluish-green colour, which is often an indication of pollution with phosphates and other fertilizers to a level that may constitute a health hazard.