202 LINDSAY, ON THE PROTOPHYTA OF ICELAND. 
Occasionally, their altitudinal range is considerable, as they 
ascend to 17,000 or 18,000 feet on the Himalayas. 
The Confervacee are an immense tribe, whose genera or 
species are more or less plentiful in a great variety of habitats 
in all parts of the world. The lower or smaller forms have 
generally the widest geographical range, and ascend to the 
greatest altitudes (17,000 to 18,000 feet on the Himalayas). 
They abound on the Antarctic Islands. Confervacee occur 
equally in salt, brackish, and fresh water ; in hot springs; on 
soil and rocks however bare, when sufficiently moist and 
shaded; and on various aquatic plants. Generally speaking, 
the branched marine species are the larger, but some of those 
which occur in mountain streams are also very long and fila- 
mentous. Not infrequently, the freshwater forms occur on 
the surface of stagnant water in masses so dense and so 
closely packed that they have obtained and deserve the name 
of “‘ water-flannel”’ or ‘‘ water-paper.” A similar mass, which 
sometimes resembles a coarse textile or felted fabric or paper, 
appears occasionally on flooded ground. Some genera or 
species contain, like various higher (Rhodospermous) Algz, 
considerable quantities of calcareous matter, which obscures 
or complicates their botanical character. 
The Batrachospermee constitute a small group of delicate 
and beautiful forms. The typical genera and species are 
mostly confined to the northern hemisphere, though some 
are cosmopolite or are very widely diffused. Certain species, 
as in the Confervacee, contain a considerable amount of cal- 
careous matter. ‘The species of the genus Batrachospermum are 
natives of fresh water, with the exception of one, which in- 
habits the sea. 
Of the Siphonee, some genera and species affect sandy 
shores, others rocks above or below high-water mark, or 
exposed only to the sea-spray; others, again, inhabit deep 
water. Some are confined to warm, but others to cold, cli- 
mates. The Vaucherie are widely distributed, occurring both 
in the southern (Kerguelen’s Land, New Zealand), and 
northern, hemispheres. They frequently abound in pools 
about waterfalls, and on damp soil or mud. Like so many 
of the lower Algz, they exhibit a wonderful power of resisting 
extremes of temperature. 
We have seen, then, that many of the Chlorospermous Alge 
are ubiquitous—that they abound in Arctic and Antarctic, as 
well as temperate and tropical, climates—that they ascend to 
great elevations—that they occur in waters of all kinds and 
temperatures, as well as in a great variety of other habitats. 
Moreover, Rabenhorst’s and other works show how plentiful 
