1. In healthy plants, of Bahia oranges budded on sour orange stock the osmotic pressure above and below the union of stock and scion is the same. 2. In diseased plants, the osmotic pressure below the union is much smaller than above. The difference of this pressure between roots of healthy and diseased plants is still more evident. 3. The osmotic pressure of the leaves of an unbudded sour orange tree is much superior than that of the caipira orange. 4. The scion seems to produce alteration on the osmotic pressure of the stock, sometimes raising and sometimes lowering it.