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Vol Vn OCTOBER, 1920 No. 8 
AMERICAN 
JOURNAL OF BOTANY 
OFFICIAL PUBLICATION OF THE 
BOTANICAL SOCIETY OF AMERICA 
( JVOV f. 
CONTENTS 
Byron'David Halsted, June 7, 1852-August 28, 191 8. 
F. L. Stevens, L. H. Pammel, and Mel T. Cook 305 
Absorption of Moisture by Gelatin in a Saturated Atmosphere. 
Charles A. Shull and S. P. Shull 318 
Slow and Rapid Growth . H. S. Reed 327 
Cytology and Systematic Position of Porphyridium Cruentum Naegeli. 
Ivey F. Lewis and Conway Zirkle 333 
Somatic Chromosomes in Tradescantia Lester W. Sharp 341 
PUBLISHED 
IN COOPERATION WITH THE BOTANICAL SOCIETY OF AMERICA 
At 41 North Queen Street, Lancaster, Pa. 
BY THE 
BROOKLYN BOTANIC GARDEN 
Brooklyn, N. Y. 
Entered as tecond-class matter February 21, 1914, at the post office at Lailcaater, PennaylTafiia, 
under the act of March 3, 1879 
