New York Agricultural Experiment Station. 331 



ment is illustrated and partly described in Bnlletin 1X6.^ Tt is 

 of iron-frame construction and is so arranged that the condi- 

 tions of light, heat and ventilation may be kept remarkably uni- 

 form throughout. The portion used for the plants is separated 

 from the walls by walks. The plants were gTown in boxes ar- 

 ranged on benches as indicated in the diagram opposite. The 

 numbers in this diagram correspond to the soil treatment num- 

 bers given in Table IV. 



the boxes. 



In testing the action of particular factors upon plants it is 

 essential that all conditions be under the best possible control 

 so that the other factors which are not being tested shall be uni- 

 form. At the same time it is desirable that the conditions of the 

 experiment conform to ordinary horticultural practice so far 

 as this can be done without lessening the reliability of the test. 

 It was decided that these conditions could best be fulfilled iu 

 these experiments by growing the plants in small wooden boxes. 

 These have an advantage over benches or sections of benches 

 in that plants receiving similar treatment may be distributed in 

 various locations in the house. With such an arrangement there 

 is a tendency to equalize in the average results any inequalities 

 which may exist in the environment in different locations in the 

 house. Moreover boxes may be easily handled for weighing or 

 photographing. The boxes were made 1.5 x 15 x 8 inches inside. 

 They were not filled quite to the top and some space at the 

 bottom was occupied with gravel for drainage so that the soil 

 in each box was about 7 inches deep, which is not far from the 

 depth of soil ordinarily found on greenhouse benches. The 

 boxes easily accommodate four lettuce plants, one near each 

 corner. 



THE SOILS. 



Both a medium clay loam and a very light sandy loam were 

 used in these experiments. Each particular treatment as regards 



"N. Y. Agr. Exp. Sta. Bui. 140 : 1G2 and PI. II; Ann. Kept. 1898 : 471 and 

 PI. XLIV. 



