Vol.111. 
OCTOBER, 1916 
No. 8 
AMERICAN 
JOURNAL OF BOTANY 
OFFICIAL PUBLICATION OF THE 
BOTANICAL SOCIETY OF AMERI 
OCT :l 
CONTENTS 
The angular micrometer and its use in delicate and accurate microscopic 
measurements Howard E. Pulling 393 
Influence of the medium upon the orientation of secondary terrestrial roots. 
Richard M. Holman 407 
The anatomy and phylogenetic position of the Betulaceae. . .Carl S. Hoar 415 
The toxicity of bog water - . .George B. Rigg 436 
On the osmotic pressure of the tissue fluids of Jamaican Loranthaceae par- 
asitic on various hosts. . . . J. Arthur Harris and John V. Lawrence 438 
Four-lobed spore mother cells in Catharinea Charles E. Allen 456 
The wandering tapetal nuclei of Arisaema F. L. Pickett 461 
Two types of variable pubescence ih plants . P. L. Ricker 470 
The seaweeds of Hawaii Vaughan MacCaughey 474 
PUBLISHED 
IN COOPERATION WITH THE BOTANICAL SOCIETY OF AMERICA 
BY THE 
BROOKLYN BOTANIC GARDEN 
At 41 North Queen Street, Lancaster, Pa^ 
Entered as second-class matter February 21, 1914, at the post office at Lancaster, Pennsylvania, 
under the act of March 3, 1879. 
