30 James Stewart Wiant 



period of four weeks. This additional shading, together with frequent 

 sprinkling, maintained a rather high soil moisture and atmospheric 

 humidity. 



The experiments at the Keene nursery were conducted on an entirely 

 different plan. Throughout both seasons it was attempted to conform in 

 every possible way to the regular nursery practices in making up and caring 

 for the beds. In order to provide for adequate replication of the various 

 treatments, the beds were divided by board partitions into continuous 

 series of small plats In the earliest experiments of 1926, these plats 

 were 12 square feet in area and were sown with a definite quantity of seed 

 distributed as evenly as possible in nine rows. For all later experiments 

 the size of the plats was increased to 16 square feet, the number of rows 

 remaining the same. The seed required for each set of three rows was 

 weighed separately, thus providing for a more nearly uniform distribution 

 than that afforded by seeding the entire nine rows from a single packet. 



Liquid treatments were made from ordinary sprinkling cans directly 

 after seeding. In some cases further treatments were made after emer- 

 gence had occurred. Half of the check plats were sprinkled with an amount 

 of water equal to that used in applying the chemicals to the treated plats. 

 Where chemicals were applied in the dry condition, the materials were 

 sifted on the plats from an envelope and worked into the upper inch of 

 soil when the beds were given the final raking. 



In the spring experiments of 1926, four replications were made of each 

 treatment and a check plat was provided for every five to seven treated 

 plats. In later tests, five replications were made and a single plat was left 

 untreated for every five which were treated. The various replicates and 

 checks were distributed over the beds as nearly uniformly as possible. 



Materials 



Aluminum sulfate, copper carbonate, mercuric chloride, mercurous 

 chloride, sulfuric acid, and a number of commercial preparations con- 

 taining organic compounds of mercury, were used at various times in the 

 course of these investigations. The source and the grades of the different 

 materials used in these experiments are given below. The descriptions 

 of the composition and the chemical properties of the various commercial 

 preparations are based upon statements of the manufacturers. The same 

 is true for the changes in composition which have been made in several of 

 the materials since the particular samples used in these tests were received. 



Aluminum sulfate of technical grade was obtained from Merck & Co., 

 of New York City, and a commercial grade was procured from the General 

 Chemical Co., of New York City. By passing the pulverized form through 

 sieves with twenty-five meshes to the inch, a fairly satisfactory material 

 was obtained for use in the experiments with dry chemicals. This product 

 was much coarser, however, than the mercury dusts. 



The sulfuric acid employed was the commercial grade of concentrated 

 acid, purchased in a local drug store. 



