Freshwater Algae 7 a 



Calcareous Deposits formed by Algae. 



Amongst the material collected were a number of pebbles from a warm 

 creek, a tributary to the Sadlerochit river, northern Alaska. The water of this 

 creek came from some warm (sulphur?) springs further inland. The samples 

 collected were pebbles of various sizes with a greenish incrustation upon the 

 exposed surfaces. An examination of the incrustation showed it to be a deposit 

 of calcium carbonate in which were embedded some blue-green algae and 

 diatoms. Calcareous and silicious sinters with algae embedded in them ars not 

 uncommon in the waters of hot springs and geysers; and the embedded algae 

 are almost exclusively members of the Myxophyceae. It is not surprising, 

 therefore, that the blue-green algae were found upon the Alaska pebbles. Here 

 Calothrix parietina was the prevailing species, but there were a few small colonies 

 of a Gloeocapsa which could not be determined specifically, and a number of 

 diatoms, mostly Epithemia turgida and E. gibba. There is no doubt that blue- 

 green algae are responsible for the precipitation of the calcium carbonate which 

 is retained in their gelatinous sheaths. However, to elucidate the precipitation 

 a careful analysis of the water and of the deposit, as well as culture experiments 

 made upon the algae under different conditions, would be needed. 



The collections of freshwater algae made by the Canadian Arctic expedition 

 add considerably to our knowledge of the distribution of species. There are a 

 number of records new to this continent or to arctic regions. Some species 

 recorded here, such as Hyalotheca mucosa, are well known in the warmer 

 temperate and subtropical regions, yet, as these new observations show, they 

 are able to thrive in some localities within the arctic circle. Cosmarium 

 Cucurbita var. attenuatum hitherto has been recorded only from England, 

 Germany, and the West Indies, and Cosmarium subexcavatum var. ordinatum 

 only from Switzerland and England, yet these and some others with very 

 limited distribution elsewhere have been found in the collections I have 

 examined. A number of species, including many species of Micrasterias, known 

 from Alaska and Greenland, were not present in the material submitted to me. 

 This seems remarkable. However, up to the present time very little attention 

 has been paid to the freshwater algae of the Dominion either in arctic regions 

 or ijn more temperate parts. Further work may show that many species, rare 

 or apparently absent in our flora, are more generally distributed than hitherto 

 supposed. 



The following is a list of all species of Myxophyceae and Chlorophyceae 

 found by the expedition. Accompanying this Ust are six columns which indicate 

 the distribution of these algae as known from records made in Alaska, arctic 

 Canada visited by the expedition, Greenland, the Faeroe islands, the United 

 States of America exclusive of Alaska, and Canada exclusive of the arctic. 

 The column for Canada exclusive of the arctic contains many new records 

 made by myself. These I hope to discuss in another communication. 



The following symbols are employed: 

 + : new record. 

 + : previously recorded. 

 - : not recorded. 

 + : an original record for Canada exclusive of the arctic not hitherto 



published, 

 t: identical in form with original type, 

 v: a variety of the species, 

 f : a form of the species. 

 *v: a variety of the species hitherto not recorded for Canada. 



