374 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
Since the nine living plants in the neutral soil were evidently 
sick and getting worse, an experiment was undertaken to determine 
whether such sick plants could be resuscitated with aluminum sul- 
phate. The nine plants were arranged in sequence, from the best to 
the poorest. To the second, fourth, sixth, eighth, and ninth was 
given 1.25 grams of aluminum sulphate each. This was immediately 
dissolved and washed into the soil by repeated syringing with water. 
Thus five of the plants made sick by the neutral soil were treated with 
aluminum sulphate and four were left untreated. 
On May 16, at the end of six weeks, the average height of the four 
sick and untreated plants was 434 inches, their older leaves were 
yellowish green, some of the leaves were scalded by the sun, and the 
latest young leaves were nearly white. The other five plants, treated 
with aluminum sulphate, had resumed normal growth, with normal 
green leaves, though the older scalded leaves still remained pale. 
Their average height was 514 inches. 
Ten weeks later, on July 26, the treated and untreated plants were 
in the condition indicated in Plate 8. The untreated plants were 
small, pale, and weak. The plants treated with aluminum sulphate 
not only had recovered from their sick condition but had put out 
new leaves, shed their old ones, and grown to twice the height of the 
other plants. 
In Plate 7 is shown, at the left, a normal healthy plant of frank- 
linia, grown continuously from February 8 to July 26, 1923, in a 
naturally acid soil made up of peat and sand. At the right is a 
plant of the same history and treatment except that it was in a 
neutral soil consisting of one part each of loam, manure, and sand. 
It was pale, sickly, and less than a third the height of the other. 
The two plates, 7 and 8, show conclusively the stimulating effect 
of soil acidity on this plant, whether the acidity is natural or is 
brought about artificially by the application of aluminum sulphate. 
EXPERIMENTS WITH BLUEBERRIES 
The aluminum-sulphate treatment has been applied to blueberry 
plants in an unsuitable soil, with the same stimulating results 
obtained in the experiments with rhododendron and franklinia. On 
February 4, 1924, 12 small seedling blueberry plants 5 months old 
were potted in 2-inch porous earthenware pots in an ordinary 
neutral greenhouse soil consisting of one part of rotted turf loam, 
one part of well-rotted cow manure, and one part of sand. On the 
following day each of them was given 1.25 grams of ground alumi- 
num sulphate. The sulphate was placed on the surface of the soil 
in the pot and was then dissolved and washed into the soil by 
repeated syringing with water. The solution of aluminum sulphate 
