80 BULLETIN OF THE BUSSEY INSTITUTION. 
long filamentous algz and fine-leaved phanerogams. No plant of our 
waters is of such large size, or of such fine meshes, as the Plectonema 
Wollet, which, although as yet recorded in only two localities, will 
probably prove common enough. It is a summer plant, and does not 
attain considerable dimensions before July. It starts on the stems, 
leaves, and old sticks on the bottom, and forms coils several feet in 
length. On reaching the surface, it expands over considerable areas. 
In the latter part of September, it breaks away from its attachments, 
drifts ashore, and disappears to return the next summer. 
In conclusion, a word about another plant common at Horn Pond, 
and which has been sent to us from several localities, with inquiry as 
to its nature. It forms a bluish or yellowish green scum on the water, 
often spread over a considerable area. Were it not that it forms such 
a thin layer, it could be collected in large quantities. Kept in bottles, 
it multiplies and forms irregular masses of a pea-green color and mealy 
consistency. At first solid, the superficial cells imbedded in a gela- 
tinous‘ mass increase rapidly, and it becomes hollow. Then certain 
portions project like buds, and finally separate from the mother plant, 
which seems to be perforated. This plant, Clathrocystis eruginosa,* 
was described by Henfrey, and is now classed by Cohn amongst the 
Bacteria, and placed near Clathrocystis roseo-persicina, a plant which 
forms purplish red films on decaying alge, and on the ground along 
our coast, and which in Europe is also found in fresh water, but 
it has not yet. been found in the interior of our own country. We 
mention it from its frequent occurrence, and because it has been sup- 
_ posed to injure the water in some places. There is no account of any 
injury having been done to man; but in Germany, where it is known 
as the Wasserbliithe, it has been destructive to fishes. Cohn 7 suggests 
that the slimy substance of which it consists, forms a coating over the 
fish, and shuts off the supply of air necessary to support life. Professor 
Hagen, of Cambridge, suggests, as a remedy, the introduction of snails 
into water where it occurs, as they are extremely voracious, and 
eat large quantities of fresh-water alge. 
* “Trans. of the Microscopical Society of London,” 1856. 
+ ‘“‘Aus neuester, wie aus alterer Zeit besitzen wir Nachrichten, dass die 
Fische in einem Teiche, welcher mit der Wasserbliithe dieser alge sich bedeckt, 
massenhaft absterben; vielleicht wird durch die dicke Schleimhaut die Auf- 
nahme des fiir das Athmen der Fische unentbehrlichen Sauerstoffs aus der Luft 
gehemmt.” Beitrage zur Biologie, Vol. 1, Part III, p. 155. 
