138 DEPAETMENTAL REPOETS. 



the proi^ortions and amounts whicli may exist without prohibiting 

 plant growth) of each salt or mixture of salts commonly found in 

 alkali soils or used as fertilizers. The influence of various concen- 

 trations of these salts or salt mixtures was noted ui)on seedlings of 

 alfalfa, white lupine, and wheat. It was found that the limits for 

 these various salts differ greatly. The idea commonly held that the 

 action of these salts is a physico-chemical one alone, and dependent 

 upon the "osmotic pressure" which they exert in the soil solutions 

 and a consequent mechanical rupture of the plant tissues, has been 

 disproved. It was shown that tlie effect of one salt in raising the 

 toxic limit of another is often very great. The importance of the lime 

 salts .n this connection was shown to be enormous, the limit for 

 magnesium chlorides being raised many times in the presence of an 

 excess of lime sulphate. These investigations open up lines of 

 work for the physiologist and for the scientific study of fertilizer 

 apjjlications. 



CHEMICAL METHODS FOR USE BY FIELD PARTIES. 



The field method for the determination of carbonates, bicarbonates, 

 and chlorides has been further studied in the laboratory, for the 

 purjjose of obviating certain mechanical difficulties which had arisen 

 in its use, and also to extend its application to other similar determi- 

 nations. It is believed that it is now in very satisfactory shape for 

 either field or laboratory use. 



COOPERATION WITH STATE INSTITUTIONS. 



As heretofore, this Division has atteropted to secure the fullest 

 possible cooperation with the State experiment stations, boards of 

 agriculture, and geological surveys. Such cooi)eration has been par- 

 ticularly close and satisfactory and mutually beneficial with the 

 Maryland Geological Survej', Maryland Agricultural Experiment 

 Station, the North Carolina Department of Agriculture, the Utah 

 Agricultural Experiment Station, and the Arizona Agricultural Exper- 

 iment Station. Other institutions have helped in various ways in 

 the preparation of plans and the securing of base maps. 



PUBLICATION OF THE REPORTS AND MAPS. 



The Fifty-sixth Congress, second session, provided by joint resolu- 

 tion, approved February 23, 1901, for the publication annually of a 

 "Report of the field operations of the Division of Soils." In accord- 

 ance with this, the report of the field work for 1900 was prepared and 

 transmitted to the Public Printer about March 1, 1901. Under the 

 contract let by him for tlie lithographic work on tlie maps, these were 

 to be delivered not later than September 1 ; but on July 4 the litho- 

 graphic establishment where they were being ]>repared was destroyed 

 by fire. Fortunately, the work had progressed so far that records of 

 all the work were jjreserved; nevertheless, the jjublication of the report 

 will necessarily be delayed, and it can hardly appear before the end 

 of the calendar year. 



As tlie work of the Bureau extends it is doubtful if the publication 

 of all the results of the field operations in one volume will be either 

 feasibh^ or econo<inical; but this is a matter which can hardly be 

 determined at this time. 



