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 irifestans. 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 



Alternaria 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 



m 



