APPENDIX.
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.