CONTENTS 
Page 
Announcement of Weekly Publication. D. F. Houston . i 
Effect of Alkali Salts in Soils on the Germination and Growth of 
Crops. Frank S. Harris . i 
Histological Relations of Sugar-Beet Seedlings and Phoma betae. 
H. A. Edson. 55 
Perennial Mycelium in Species of Peronosporaceae Related to 
Phytophthora infestans. I. E. Melhus. 59 
Hibernation of Phytophthora infestans in the Irish Potato. I. E. 
Melhus. 71 
Enzyms of Apples and their Relation to the Ripening Process. 
R. W. Thatcher. 103 
An Automatic Transpiration Scale of Large Capacity for Use 
with Freely Exposed Plants. Lyman J. Briggs and H. L. 
Shantz. 117 
Parasitism of Comandra umbellata. George Grant Hedgcock. .. 133 
Separation of Soil Protozoa. Nicholas Kopeloff, H. Clay 
Lint, and David A, Coleman. 137 
Effect of Temperature on Movement of Water Vapor and Cap¬ 
illary Moisture in Soils. G. J. Bouyoucos. 141 
Soil Temperatures as Influenced by Cultural Methods. Joseph 
Oskamp. 173 
Altemaria panax, the Cause of a Root-Rot of Ginseng. J. Rosen¬ 
baum and C. L. Zinnsmeister. 181 
Some Potato Tuber-Rots Caused by Species of Fusarium. C. W. 
Carpenter. 183 
Infection Experiments with Timothy Rust. E. C. Stakman and 
Louise Jensen. 211 
Experiments in the Use of Current Meters in Irrigation Canals. 
S. T. Harding. 217 
Relation of Sulphur Compounds to Plant Nutrition. E. B. Hart 
and W. E. ToTTingham. 233 
Distribution of the Virus of the Mosaic Disease in Capsules, Fila¬ 
ments, Anthers, and Pistils of Affected Tobacco Plants. H. A. 
Allard. 251 
Dissemination of Bacterial Wilt of Cucurbits. Frederick V. 
Rand. 257 
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