78 BULLETIN OF THE BUSSEY INSTITUTION. 
before, and which was first observed by the Rey. Francis Wolle in the 
waters near Bethlehem, Pa. It grew in great abundance at the head 
of the pond where the water was shallow, attached to other plants 
and sticks, and spread over the surface in areas of several square feet, 
forming blackish green patches like the plant called mermaid’s hair 
(Lyngbya majuscula) on the sea coast, only very much more luxuriant. 
Where the Plectonema was free from the slimy substance, it emitted 
the suffocating smell of many of the Oscillarie, but was free from the 
pig-pen odor. 
In various places along the edge of the pond, and in some places 
where the Plectonema came to the surface, were masses of slime, at 
first of a pale bluish-green, afterwards of a brownish color. The 
odor was most disgusting, and resembled rotting horse-dung to such 
an extent that it was difficult to believe that it came from a vegetable 
substance. A microscopic examination showed that the slime was 
composed of an amorphous mucus, in which were the threads composed 
of the heterocysts and hormogoniz peculiar to the Vostocs proper, but, 
unfortunately, in a too advanced stage of decomposition to be specifi- 
cally determined. An examination of the water of the pond showed 
it to be full of little rods, which shone in the sunlight. These rods 
had the same microscopic structure as the filaments of the slimy 
masses which were evidently aggregations of decaying filaments, which, 
in a normal condition, float freely in the water. At the time of our 
visit, however, even the filaments which were still floating, were so far 
disintegrated that, after an unavoidable journey of several hours in 
the cars, they were not in a condition to be specifically. determined. 
We are entitled to assume that the alga was a species of Anabena or 
some nearly related genus, perhaps Nodularia litorea, Thuret, the de- 
composition of large quantities of which produced an intensely disa- 
greeable odor near Deauville, Normandy, in August, 1874, as we 
learn from Dr. Bornet. 
Early in October, we again visited Horn Pond, with the purpose of 
obtaining some of the Anabena, if possible. It had, however, com- 
pletely disappeared. Furthermore, the Plectonema, which in August 
was attached, was washed ashore in immense quantities, leaving the 
surface of the pond clear. <A quantity of the Plectonema was kept for 
some time until it began to decay, when that too began to give off an 
odor of pig-pen, which could hardly have arisen from any remains of 
