236 Rhodora [DECEMBER 
NOTES ON THE ALGAE OF THE RIDEAU, ONTARIO. 
A. B. Krvau, M. A. 
Tuar Rideau canal system runs from Kingston, Ontario, to Ottawa, 
the route being by way of the Cataraqui River, a chain of lakes and 
the Rideau River. In July, August and September, 1911, the writer 
made a reconnaissance of the Algal-flora of these waters as far as Lake 
Opinacon, some forty miles from Kingston. Most work was done at 
Kingston Mills, seven miles up from Kingston, and at Lake Opinacon. 
The following is presented merely as a preliminary list, the species 
marked with an asterisk being here recorded from Canada for the first 
time. 
CYANOPHYCEAE. 
Aphanothece microscopica, Naegeli. Among other Algae on stones 
and snags in Lake Opinacon. 
Microcystis marginata, Kuetzing. As plankton in Lake Opinacon. 
Coelosphaerium kuetzingianum, Naegeli. Common as plankton in 
Lake Opinacon. The main constituent of a very dense “ Water- 
bloom" on parts of the “Lake of Sticks" just above the locks at 
Kingston Mills on September 11th. 
* Anabaena flos-aquae, Brébisson. Forming a “ Water-bloom," in 
basin off the upper lock at Kingston Mills, July 15th. 
*Dichothrix hosfordii, Bornet. Common on submerged rocks in 
Lake Opinacon. 
Rivularia pisum, Agardh. On drifting water-plants at Jones’ 
Falls. On leaves of Potamogeton amplifolius in Lake Opinacon. 
*Rivularia incrustata, De Toni. Forming gelatinous nodules on 
stems of Scirpus americanus near the mouth of the Cataraqui River, 
July 22. 
CHLOROPHYCEAE. 
Spirogyra weberi, Kuetzing. In the Cataraqui River near its mouth. 
This material was so abundantly fruited that it was difficult to find 
a vegetative cell. 
Nephrocytium agardhianum, Naegeli. Among plankton in Lake 
Opinacon. 
