Smithsonian Report, 1926.—Coville PLATE 13 
STIMULATING EFFECT OF A NATURALLY ACID SOIL ON A RHODODENDRON 
In early May healthy seedlings of Rhododendron marimum were set in 2-inch pots in an ordi- 
nary fertile garden soil composed of equal parts, by bulk, of loam, well-rotted cow manure, 
and sand. Other similar plants were potted in 2 parts of upland peat tol ofsand. In June 
of the following year, when the photograph was made, the plant at the left, in the neutral 
garden soil, had made no growth, while the plant at the right, in the strongly acid peat soil, 
had made normal and luxuriant growth. It is better, whenever practicable, to give acid- 
soil plants a naturally acid soil than to put them in a neutral soil and then acidify it artifi- 
cially with aluminum sulphate. Natural size 
