By cutting to different depths the roots of Pinus silvestris in the podsolised soil of a heath pinewood in Aberdeenshire, Scotland, the weight of crop of both the deep rooting Deschampsia flexuosa and the shallow rooting Oxalis acetosella increases with depth of cut. The same results on Oxalis are got by cutting the roots of beech on the same soil. Water added to the surface and at 10 cm. and 20 cm. from the mineral soil surface produce crop weights similar to the control. With greater depth of cut the foliage of Deschampsia and Oxalis becomes darker green and generally the number of flowering shoots of Deschampsia increases, although in the deepest cut many abort. The N% in Deschampsia also increases with depth of cut up to a certain point. The experiment shows that the deeper lying pine roots affect the vigor of both the deep-rooting Deschampsia and the shallow-rooting Oxalis and raises afresh the concept of edaphically complementary species.