26 EXPERIMENTS IX BLUEBEEEY CULTUEE. 



was 6 inches, and at the end of the season 12^ inches. In the second 

 lot, in which the proportion was peat 3. mold 5. sand 1, and loam 1, 

 the average height on ]May 29 was 44 inches, and at the end of the 

 season llf inches. It will be observed that these two lots of plants 

 are intermediate in their growth between the first two and that in all 

 four lots the povert}" of growth is roughly proportional to the amount 

 of leaf mold used in the soil. 



That the weak growth of the plants in leaf mold was not caused by 

 a compacting of the soil and a lack of aeration, due to too small a 

 proportion of sand in the mixture, is shown by still another lot of 25 

 plants which were potted in a soil mixture having the proportion of 

 mold 6, sand 3. and loam 1. These plants averaged only 4 inches in 

 height on May 29 and 6^ inches at the end of the season. They grew 

 even less, therefore, than the plants with only 1 part of sand and 8 

 parts of mold. 



In Plate II. from a photograph made in the winter of 1909-10. is 

 shown a flat divided into three parts and set on February 10, 1909, 

 with blueberr}' seedlings of uniform size. The soil in the middle 

 compartment is a mixture of leaf mold 8 parts, sand 1 part, and loam 

 1 part. In the compartment to the left the soil is in the proportion 

 of kalmia peat 8. sand 1. and loam 1: and in the right-hand com- 

 partment, kalmia peat 4. leaf mold 4, sand 1. and loam 1. It will be 

 observed that the greater the amount of leaf mold the poorer the 

 growth of the blueberry plants. 



The reason for the unexpected deleterious effect of leaf mold, as 

 shown by these experiments, is given on page 29 and further discussed 

 on page 35. 



(6) The swamp blueberry does ^*0T thrive in soils having a neutral or 



ALKALINE REACTION, JiVT FOE VIGOROUS GROWTH IT REQUIRES AN ACID SOIL. 



The consideration of this statement requires first an understanding 

 of the means used to determine whether a soil is acid or alkaline. 

 The simplest means is the litmus test. 



While one may become sufficiently expert in the use of the litmus 

 test to form a fair judgment of the degree of alkalinity or acidity in 

 a soil, an exact determination requires some different method. It 

 was found that for the weak acids prevalent in the peat soils to the 

 examination of which the present experiments led. the phenol- 

 phthalein test was the most satisfactory. If a few drops of phe- 

 nolphthalein indicator be added to a solution, the solution, if 

 alkaline, turns instantly pink, and if acid or neutral its color does 

 not change. The application of this phenomenon to the determina- 

 tion of the degree of acidity of an acid solution is as follows: A 

 definite amount of the solution, usually 100 cubic centimeters, is 

 placed in a beaker, a few drops of an alcoholic solution of phenol- 



193 



