SOME PECULIAR VARIETIES OF ALG.E 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- 

 chodesminm 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. At a 

 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 



