HANDBOOK OF SEA-WEEDS. 23 



are found not only in water, but also on the moist surface of the 

 ground and on other plants, in hot springs and amid polar ice. 

 They are said to occur in such countless myriads in the South 

 Polar Sea as to stain the berg and pack ice wherever these are 

 washed by the surge. A deposit of mud, chiefly consisting of 

 the shells of Diatoms, 400 miles long, 120 miles broad, and of 

 unknown thickness, was found at a depth of between 200 and 400 

 feet on the flanks of Victoria Land in 70 south latitude. Such 

 is their abundance in some rivers and estuaries that Professor 

 Ehrenberg goes the length of affirming that they have exercised 

 an important influence in blocking up harbours and diminishing 

 the depth of channels. The trade and other winds distribute large 

 quantities over the earth, which may account for the universality 

 of their specific distribution ; for Sir Joseph Hooker found the 

 Himalayan species to closely resemble our own. Common British 

 species also occur in Ceylon, Italy, Virginia, and Peru. The 

 typical species of the Confervaceae are also distributed over the 

 whole surface of the globe. They inhabit both fresh and salt 

 water, and are found alike in the polar seas and in the boiling 

 springs of Iceland, in mineral waters and in chemical solutions. 

 Some of the tropical ones are exceedingly large and dense. 

 Batrachospermum vagum, in the next tribe, a native of England, 

 is also found in New Zealand. An edible species of Nostochinese, 

 produced on the boggy slopes bordering the Arctic Ocean, is 

 blown about by the winds sometimes ten miles from land, where 

 it is found lying in small depressions in the snow upon the ice. 

 The common Nostoc of moist ground in England occurs also in 

 Kerguelen's Land, high in the southern hemisphere. Floating 

 masses of Monormia are often the cause of the green hue assumed 

 by the water of ponds and lakes. Certain species of Oscillatoria 

 of a deep red colour live in hot springs in India, and the Red 

 Sea is supposed to have derived its name from a species of this 

 tribe, which covers it with a scum for many miles, according to 

 the direction of the wind. The lake of Glaslough in County 

 Monaghan, Ireland, owes its colour and its name to Oscilla- 

 toria serugescens, and large masses of water in Scotland and 

 Switzerland are tinted green or purple by a similar agency. 

 A few species of Siphonese have a very wide range, two British 

 species of Codium occurring in New Zealand. The Ulvacese 

 abound principally in the colder latitudes. Enteromorpha intes- 

 tinalis, a common British species, is as frequent in Japan, where 

 it is used, when dried, in soup. The Rhodosperms are found in 

 every sea, although the geographical boundaries of genera are 

 often well-marked. Gloiosiphonia, one of our rarest and most 



