
AQUATIC PLANTS OF FRESHWATER 

or in the heated water of a boiling spring. They are the last vestige of 
life in the region of perpetual snow or in the heated basin of the geyser. 
The numerous forms are to be found in every stagnant pool and ditch, 
rivulets,'springs and in all other bodies of water. In pools and ponds the 
most conspicuous forms are Oscillatorie and Zygnemacix; the former 
forming dense floating or attached slimy strata, having fine rays extending 
from the mass, of dark green, purplish or bluish-black color. The 
Zygneme are bright green filamentous masses, usually entangled among 
the water plants, twigs, etc. When in fruit they become dingy, yellowish, 
or dirty looking. Late in the season Rivulareee and Nostocs are often 
met with. These adhere to larger plants and floating matter and form 
fine fringes around the stems and edges of the leaves, or little green and 
brownish globules and small protuberances. Of the river Algz, the 
Desmids are abundant in the spring and summer months, adhering to 
rocks and water plants; and Chetophora, Scytonema and Palmela are also 
numerous, often free but sometimes attached to objects in the water. 
Diatoms are also classed in the family of Algz and consist of minute 
silicious organisms which were formerly considered as belonging to the 
lowest forms of animal life. They are a higher form of Algz and obtain 
firmness by depositions of silica. Another class, the Acetabularie, deposit 
carbonate of lime. 
The mentioned Algex and Conferve are those with which the aquariist 
becomes familiar, the group being too complex in classification for further 
description in a work of this character. The common small aquarium 
species are mentioned elsewhere as they have more or less parasitic character. 
Alge have many useful purposes in the aquarium, as they forma 
screen on the glass to intense light, serve as a natural food for both the 
fishes and the scavengers, and have beneficial medicinal properties to fishes. 
When the growth is of a clear green color and not so thick as to be un- 
sightly, it may be left undisturbed on the glass or removed only from the 
side through which the contents are viewed;. but when the growth, both 
on the glass and in the water, assumes a brown color, it is indicative of 
a dead and decaying condition and it is advisable to thoroughly clean the 
aquarium and refill with fresh water, as the appearance of the alge isa 
good indication of the water conditions. Excessive growth on the plants 
is injurious and they should be cleaned to prevent suffocation or the 
affected leaves removed, but usually the fishes and scavengers, when not 
overfed, keep them sufficiently clean. It is for this purpose that gold- 
fishes are kept in tanks with aquatic plants by florists, to keep down both 
objectional plant and injurious insect life. 
Should the growth become so excessive as to destroy the lower leaves 
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