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PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE BOTANICAL SOCIETY OF WASHINGTON 



The 104th regular meeting of the Botanical Society of Washington 

 was held at the Cosmos Club on the evening of Tuesday, April 6, 1915. 

 Forty-five members and fifty-three guests were present. The following 

 papers were read : 



Prepaleozoic 'algal deposits: Charles D. Walcott. Mr. Walcott 

 described the stratigraphic position of the great Prepaleozoic Beltian 

 series of central Montana, which he considered to be of fresh or brack- 

 ish water origin, in all probability deposited in a great inland lake or 

 lakes covering an area of about 6,000 square miles, and also on river 

 flood plains as sand and gravel, or perhaps as fine dust carried by winds. 

 The formations consist of sandstones, calcareous and siliceous shales, 

 and beds of limestone, the last varying in thickness from a few inches 

 to several thousand feet. The same type of deposits also occurs in the 

 Grand Canyon region of Arizona and extends northward along the 

 main ranges of the Rocky Mountains far into Alberta and British 

 Columbia. 



At a horizon approximately 9000 feet below the bpse of the Cambrian 

 numerous reefs of algal deposits occur at several horizons in the New- 

 land limestone formation of the Beltian in Montana, and isolated 

 conci'etionary-like forms occur scattered at various levels in the over- 

 lying Spokane shales of the Belt Mountains. The algal remains occur 

 in many forms, some of which are surpi'isingly similar to those of the 

 fresh-water lake and stream blue-green algal deposits of Pennsylvania, 

 New York, Michigan, etc. Others are similar in appearance to the 

 blue-green and green algal deposits of the thermal waters of the Yellow- 

 stone National Park. 



Mr. Walcott illustrated by lantern slides the various forms of algal 

 deposits as they are found in the Pre-Cambrian rocks and in recent 

 deposits. Photographs of thin sections of both the fossil and recent 

 deposits showed similar chains of cells which are characteristic of the 

 blue green alga. Other photographs illustrated recent bacteria and 

 those associated with the algal remains in the Prepaleozoic of Montana. 

 These included the Micrococci, with both round and oval cells. Some 

 of the sections appear to carry rodlike bacilli. 



The alga] flora of some Eocene shales: Charles A. Davis. Extensive 

 beds of petroleum yielding shales of Eocene age occur in northwestern 

 Colorado and westward. They are carbonaceous, and when fresh 

 are dark brown, hard, tough and compact, with a bituminous odor. 



649 



