376 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
them out of their dormancy. After 11 weeks in the chilling frame 
they were transferred to a greenhouse maintained at an ordinary 
summer temperature. On September 23, after three months’ ex- 
posure to a temperature highly favorable to growth, the plants 
treated with aluminum sulphate were all in full leaf and in a 
healthy, vigorous condition. Of the six untreated plants four were 
dead. The better of the two remaining plants and the best of the 
seven aluminum-sulphate plants are shown in Plate 10. The alumi- 
num-sulphate plant was 18 inches high, and its healthy condition was 
indicated not only by its appearance of general vigor but by the 
flowering buds that had been formed in anticipation of its next year’s 
fruiting. The untreated plant was 5 inches high and the live part 
had a height of only 214 inches. Such leaves as were present were 
small and pallid, and it was evident that death could not be far away. 
This experiment shows conclusively that potted blueberry plants, 
which die in an ordinary fertile but neutral soil, can be made to 
thrive in such a soil after it has been acidified by a suitable applica- 
tion of aluminum sulphate. The plants used in this experiment were 
highbush blueberry, Vaccinium corymbosum. 
To determine whether a blueberry plant that is near the death 
point in a fertile but neutral soil can be resuscitated through the 
acidification of the soil with aluminum sulphate, 8 grams of this 
substance was apphed on March 31, 1926, to each of two sickly plants 
in 4-inch pots. One of the plants was already so far gone that it 
afterwards died. ‘The other plant, 414 inches high at the beginning 
of the treatment, responded to the acidification, started into active 
growth, and by September 23 had reached the condition of health 
and vigor shown in Plate 11: The old stems, although their tips 
were dead, had put out new lateral branches, and a new shoot from 
the base of the plant had grown to the height of 8 inches. The 
resuscitation was definite, complete, and unmistakable. 
EXPERIMENTS WITH HYDRANGHA 
An experiment was made by the writer in 1923 and 1924 to deter- 
mine whether the change in color of the flowers of the house hy- 
drangea, Hydrangea opuloides, from pink to blue can be brought 
about by growing the plants in an acid soil. The experiment showed 
that this could be done and that soil acidity was the cause of this 
curious and conspicuous color change. While the experiment was in 
progress, however, C. H. Connors, of the New Jersey State Agricul- 
tural Experiment Station at New Brunswick, published similar re- 
sults from experiments that he had undertaken earlier and inde- 
pendently.* An account of my own experiment, therefore, has never 
#“The control of color in hydrang:1,’’ Florists Exchange, vol. 57, pp. 1563 and 
1564, May 17, 1924. 
