TABLE OF CONTENTS 



On triple hybrids ------- 



Periodicity in Spirogyra - 



On the pollen of Microcachrys tetragona (with plates 



I and II) - 



A vegetative mutant, and the principle of homoeosis 



in plants. Contributions from the Ames Botani- 



PAGE 



Hugo de Yries i 

 W. F. Copeland 9 



Robert Boyd Thomson 26 



cal Laboratory No. 9 (with nineteen figures) 



Robert Greenleaj Leavitt 30 



■Sefier 85 



Robert F. Griggs 127 



Relation of soil and vegetation on sandy sea shores 



(with twelve figures) - J 



Some aspects of amitosis in Synchytrium (with plates 



III and IV) 



Vascular anatomy of the seedling of Microcycas calo- 

 corna. Contributions from the Hull Botanical 

 Laboratory 122 (with plates V and VI) - Helen Angela Dorety 139 



Mitosis in Fucus. Contributions from the Hull Bo- 

 tanical Laboratory 124 (with plates VIII-XI) - Shigeo Yamanouchi 173 



The reduction division in the microsporocytes of 



Agave virginica (with plates XII-XIV) - - John H. Schafjner 198 



Spermatogenesis in Dioon edule. Contributions from 

 the Hull Botanical Laboratory 125 (with 

 plates XV-XVIII and three figures) - -" Charles J. Chamberlain 215 



Undescribcd plants from Guatemala and other Cen- 

 tral American Republics. XXXI (with one figure) John Donnell Smith 253 



Comparative histology of fruits and seeds of certain 



species of Cucurbitaceae (with fifty-three figures) Kate G. Barber 263 



The anatomy of Isoetes. Contributions from the Hull 



Botanical Laboratory 126 

 XXI) - 



XIX 



The megasporophvll of Saxegothaea and Micro- 



Alma G. Stokey 311 



XXI-XXV) - - Robert Boyd Thomson 345 



Studies on the oxidizing powers of roots 



Oswald Schreiner and Howard S. Reed 355 



Bog toxins and their effect upon soils (with two 

 figures) 



Alfred Dachnowski 389 



