Vol. VII No. 13 



July 19, 1917 



JOUENAL 



OF THE 



WASHINGTON ACADEMY 



OF SCIENCES 



BOARD OF EDITORS 

 N. Ernest Dorset Adolph Knopf A. S. Hitchcock 



BUBEAU Or 8TANDAr.ES GEOLOGICAL SURVEY BUREAU 07 PLANT ENDUSTBT 



' PUBLISHED SEMI-MONTHLY 

 EXCEPT IN JULY, AUGUST, AND SEPTEMBER, WHEN MONTHLY 



BT THE 



WASHINGTON ACADEMY OF SCIENCES 



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WILLIAMS & WILKINS COMPANY 



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Entered as second-class matter July 14, 1911, at the post office at Baltimore, Maryland, under the Act of 



July 16, 1S94 



