TABLE OF CONTENTS, VOLUME VI, 1919 
No. I, January 
PAGE 
Biologic specialization in the genus Septoria (with thirteen text figures 
and Plate I) Walter Spurgeon Beach i 
A consideration of certain pathologic conditions in Ambrosia trifida 
(with one text figure and Plate II) Alb an Stewart 34 
No. 2, February 
Crytandreae Hawaiienses, Sections Schizocalyces Hillebr. and Chaeto- 
calyces Hillebr. (with Plates III-VIII) Joseph F. Rock 47 
The ecologic foliar anatomy of some plants of a prairie province in central 
Iowa (with Plates IX-XIV) Ada Hayden 69 
No. 3, March 
The ecologic subterranean anatomy of some plants of a prairie province 
in central Iowa (with plates XV-XXVIII) Ada Hayden 87 
Studies concerning the evolutionary status of polycotyledony (with six 
text figures) John T. Buchholz 106 
The role of sedges in some Colorado plant communities (with two text 
figures) Francis Ramaley 120 
No. 4, April 
The influence of light upon the action of stomata and its relation to the 
transpiration of certain grains (with eighteen text figures) 
John GUiW and George J. Peirce 131 
The origin and nature of the mucilage in the cacti and in certain other 
plants Francis E. Lloyd 156 
The influence of phosphates on the action of alpha-crotonic acid on 
plants (with nine text figures) ... .J. J. Skinner and F. R. Reid 167 
No. 5, May 
Osmotic pressures in the potato plant at various stages of growth 
(with two text figures) B. F. Lutman 181 
Cyrtandreae Hawaiienses, Sect. Microcalyces Hillebr. (with Plates 
XXIX-XXXII) Joseph F. Rock 203 
No. 6, June 
A study of plastids and mitochondria in Preissia and corn (with plates 
XXXIII and XXXIV) W. C. Twiss 217 
iii 
