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 Atlantic, called the Sargasso Sea, he sails into a vast undulating marine [pg034] prairie. Farther than the eye can reach is spread a yellowish-brown vegetation which covers the water as grass covers the plain. Sometimes these weeds are so thick as to impede navigation, and, seen from a little distance, seem substantial enough to walk upon. At other times, according to seasons and conditions of storm and wind, they are divided into strips or into island-like masses, with spaces of clear water between. If the sailor did not know the special conditions existing here he might suppose he had come upon dangerous shallows; or were the waters less turbulent he might dream that he was floating among the water-weeds of an inland lake. This vast acreage of vegetation, as large as the continent of Europe, lying southwest of the Azores and extending between the Canary and the Cape Verde Islands, was first reported by Columbus, and takes its name from the floating plant of which it is composed, the /Sargassum bacciferum/, a species of the order /Fucaceæ/, commonly known as gulfweed. Columbus's sailors took fright at the marvelous appearance and wished to turn back, thinking they had reached the end of the navigable ocean. They thought, if land were beyond, it was guarded by shoals, and that the weeds concealed dangerous rocks. Columbus threw out two hundred fathoms of line, but did not reach bottom, and continued on his course for fifteen days before emerging into clear water. From that day to this the Sargasso Sea has attracted the attention of all navigators. It is especially interesting to scientists. The physicist finds there the phenomenon of the ocean currents holding in a vortex this immense mass of seaweed, the zoölogist finds a great pasture in whose protecting shelter are living and breeding countless numbers of marine animals, and the botanist is puzzled because the source of this species of plant is clouded with doubt. [Illustration: PLATE II. Macrocystis pyrifera. Agarum Turneri. Nereocystis Lütkeana.]