SOME PECULIAR VARIETIES OF ALG 33 
a fossiliferous bed of diatoms, which measures twenty to eighty 
feet in depth and several miles in length. 
Associated with diatoms, in fresh water, are desmids, which 
are green in color and resemble the diatoms except in having a 
cartilaginous instead of a silicious covering. Another minute 
organism, Pyrocystis noctiluca, is luminous and is said to produce 
the beautiful phosphorescent effects seen in tropical seas. Tri- 
chodesmium is a little alga which periodically occurs in great 
numbers, giving the water a red appearance, as in the Red Sea, 
which is said to derive its name from this circumstance. 
RED SNOW 
In the high latitudes of the arctic regions, also on snowy moun- 
tains at altitudes where all vegetable life is supposed to be 
extinguished, there sometimes appears a redness on the surface 
of the snow, which in some cases extends for many miles. Ata 
certain place in Greenland the color was so vivid that an arctic 
voyager named the locality the Crimson Bluffs. 
The strangeness and almost sudden appearance of this color in 
the snow have been so unaccountable to uninformed observers 
that it has been ascribed by them to the falling of bloody snow 
and has been regarded with superstition. The redness is caused 
by the growth of one of the smallest of plants, the Protococcus 
nivalis. It is a simple one-celled alga containing protoplasm 
and endochrome (red coloring-matter). It grows by cell-division, 
the cell dividing into four, eight, or sixteen parts on a quaternary 
scale. Each part acquires a new covering while within the 
mother cell, and when it emerges it is a complete individual 
and ready to repeat the process. Only a few hours are required 
for its growth and development; hence its increase is rapid, and 
it requires but a little time to make itself manifest in those places 
where the conditions are favorable to its existence. 
THE SARGASSO SEA 
When the voyager reaches a certain region of the North Atlan- 
tic, called the Sargasso Sea, he sails into a vast undulating marine 
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