AUG 11 '^i^RocEEDINGS 



OF THE 



American Philosophical Society 



HELD AT PHILADELPHIA 



FOR PROMOTING USEFUL KNOWLEDGE 

 Vol. LX. 1921. No. 1. 



CONTENTS 



PAGE 



The Origin and Distribution of the Genera of the Fishes of South 

 America West of the Maracaibo, Orinoco, Amazon and Titicaca 

 Basins. By Carl H. Eigenmann --------- i 



Growth in Trees. By D. T. Macdougal -------- 7 



The Action of Bases and Salts on BiocoUoids and Cell-Masses. By 



D. T. Macdougal ------------- 15 



A Natural Group of Unusual Black Oaks. By William Trelease 31 

 The Fixed Glacial Anticyclone Compared to the Migrating Anti- 

 cyclone. By William Herbert Hobbs ------ 34 



Obituary Notices of Members Deceased : Joseph George Rosen- 



GARTEN ----------------- iii 



PHILADELPHIA 



THE AMERICAN PHILOSOPHICAL SOCIETY 



104 South Fifth Street 



1921 



