3 
i 
Igog] ATKINSON—FUNGUS PARASITES OF ALGAE 329 
at the base in the host cell. Apex opening by a single pore. Zoospores two to 
four in a zoosporangium, oval, uniciliate, with a single oil drop, 2.5 « in diameter. 
On Spirogyra varians in the vicinity of Ithaca, N. Y. 
Zoosporangiis obpyriformibus, 5—6  latis, apice una lata papilla, basi fila- 
mentis brevibus radiciformibus. Zoosporis ovoidis, 2.5 #, una guttula hyalina 
et cilio simplici attenuato praeditis. 
LAGENIDIUM RABENHORSTIS 
This species was first found in a species of Spirogyra in a stream 
of slow-running water in the valley south of the city of Ithaca. Ithas 
since been found in various species and appears to be quite common. 
The fungus attacks the vegetative cells and those just about to con- 
jugate. The zoospore enters the cell wall by a small perforation, the 
slender entrance tube growing usually nearly to the center of the host 
cell, where it enlarges to the size of the vegetative thread of the 
parasite. The general course of the threads is parallel with the axis 
of the spirogyra cell, though frequently tortuous and curved, with 
here and there short branches. The threads are usually stout, varying 
in diameter from 3 to 8. At the ends of the cell of the host they 
curve around and frequently extend back to the other end, one to 
three and four threads thus lying in a single cell. The protoplasm 
possesses numerous highly refringent granules and there are also 
vacuoles at short distances. In other cases the thread may be strongly 
curved, or even coiled at various points within the end of the cell. 
The chromatophores of the spirogyra are broken down and usually 
adhere to the threads of the fungus here and there, giving portions 
of them a green appearance in the early stages, and later a greenish 
brown as the chlorophyll becomes more and more disorganized. All 
traces of the chlorophyll at length disappear, and the fungus, lying 
in a disorganized mass of transparent protoplasm, is then seen 
distinctly throughout its entire length. In other cases the fungus 
thread may be permanently soiled by the brownish matter of the 
disorganized chlorophyll. 
The exit tubes are developed from the ends of the threads, or from 
the ends of the short lateral branches, or from the side of the main 
0 * Zopr, W., Ueber einen neuen parasitischen Phycomyceten aus der Abtheilung der 
sporeen. Bot. Verein Prov. Brandenburg 20:77—80. 1878. See also, Zur Kennt- 
