138 PHOTO-MICROGRAPHS. 
known as chlorophyl is present, and not in the 
other. Moreover, the Algz are all water-plants ; 
and in their growth they appropriate directly in- 
organic materials held in solution in the medium 
in which they live. On the other hand, the Fungi 
are chiefly air-plants; and they derive their suste- 
nance for the most part from other plants, which 
they infest as parasites, or from organic material 
supplied by the tissues of plants and animals un- 
dergoing decomposition. 
The green coloring matter referred to (chloro- 
phyl) cannot commonly be distinguished in the 
minute alge known as Bacteria; but in the larger 
unicellular alge, the green color is very pro- 
nounced. In the autumn, when the approach of 
cold weather interferes with the active life of these 
little plants, this green color frequently changes to 
aruby red. In certain species, this red color of the 
protoplasm is a constant character. This is true 
of Protococcus mvalis, which is found upon the snow 
in the arctic regions and upon snow-covered moun- 
tains in lower latitudes, where it sometimes exists 
in such abundance as to give the snow the appear- 
ance of being covered with blood. 
The life-history of these unicellular algee is not 
so simple as is that of the Aferococc’, — in which, so 
far as we know, the only mode of multiplication 
is by binary division. This mode of reproduction 
occurs, as seen in the figure. But we have an- 
other mode of reproduction among these lowly 
plants, also observed among unicellular animal 
organisms, which is very remarkable, and is essen- 
