







Vol. XL VII 



No. i 



THE 



January 1909 



JOHN M. COULTER and CHARLES 



CONTENTS 



On Triple Hybrids 



Hugo de Vries 



Periodicity in Spirogyra 



W. F. Copeland 



On the Pollen of Microcachrys tetragona 



Robert Boyd Thomson 





A Vegetative Mutant, and the Principle of Homoeosis in 



p. Robert Greenleai Leavitt 



Briefer Articles 



Longevity of Seeds 

 Respiration Calorimeter 

 Crataegus in Colorado 



William Crocker 



George J. Peirce 



Francis Ramaley 



Current Literature 





The University of Chicago 



CHICAGO and NEW YORK 

 William Wesley and Son, Londoe 



