Gemiasma verdans and Gemiasma rubra collected Sept. 10, 1882, on
Washington Heights, near High Bridge. The illustrations show the manner
in which the mature plants discharge their contents.
Plate VIII. A, B, and C represent very large plants of the Gemiasma
verdans. A represents a mature plant. B represents the same plant,
discharging its spores and spermatia through a small opening in the cell
walls. The discharge is quite rapid but not continuous, being spasmodic,
as if caused by intermittent contractions in the cell walls. The
discharge begins suddenly and with considerable force--a sort of
explosion which projects a portion of the contents rapidly and to quite
a little distance. This goes on for a few seconds, and then the cell is
at rest for a few seconds, when the contractions and explosions begin
again and go on as before. Under ordinary conditions it takes a plant
from half an hour to an hour to deliver itself. It is about two-thirds
emptied. C represents the mature plant, entirely emptied of its spore
contents, there remaining inside only a few actively moving spermatia,
which are slowly escaping. The spermatia differ from the spores and
young plants in being smaller, and of possessing the power of moving and
tumbling about rapidly, while the spores of young plants are larger
and quiescent. D, E, F, and G represent mature plants belonging to the
Gemiasma rubra. D represents a ripe plant, filled with spores, embryonic
plants, and spermatia. E represents a ripe plant in the act of
discharging its contents, it being about half emptied. F represents
a ripe plant after its spore and embryonic plant contents are all
discharged, leaving behind only a few actively moving spermatia, which
are slowly escaping. G represents the emptied plant in a quiescent
state.
Figs. A, B, C represent an unusually large variety of the Gemiasma
verdans. This species is usually about the size of the rubra. This
large variety was found on the upper part of New York Island, near High
Bridge, in a natural depression where the water stands most of the
year, except in July, August, and September, when it becomes an area
of drying, cracked mud two hundred feet across. As the mud dries these
plants develop in great profusion, giving an appearance to the surface
as if covered thickly with brick dust.
These depressions and swaily places, holding water part of the year, and
becoming dry during the malarial season, can be easily dried by means
of covered drains, and grassed or sodded over, when they will cease to
grow; this vegetation and ague in such localities will disappear.
The malarial vegetations begin to develop moderately in July, but do not
spring forth abundantly enough to do much damage till about the middle
of August, when they in ague localities spring into existence in vast
multitudes, and continue to develop in great profusion till frost comes.
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