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form set of trees is required, for instance, for a formal roadside planting, cultivar trees should be raised on stock from selected seed or, better, on vegetatively propagated stock. For the latter method two types of stock are commonly used in the West. In East Malling, England, a virus-free stock was developed known as 'Malling 12/1', or 'MF12/1'. It is vegetatively propagated by earthing up, which involves covering it with soil, thus inducing side shoots to take root. 'MF12/1' gives a less extreme but still quite vigorous growth. This stock is known for its deep and spreading anchorage roots that set the tree firmly in the ground. It makes a straight, practically unbranched stem. A weak point of this stock is its sensitivity to a root bacterium, Agrobacterium tumefaciens, which causes a cancerlike, swelling disease that finally obstructs the transport function of the roots. The occurrence of this bacterium is limited though to certain soils. A second English stock is Prunus 'Colt', procured from a cross between P. avium and the Chinese cherry, P. pseudo-cerasus. This virus-free stock is propagated by earthing up and forms a firm root system. In the field it is recognized by its mass of leaves and the many aerial roots seen on the stem. Buds grafted on this stock strike in remarkably high percentages, but a doubtful hardiness has been reported from regions with more severe winters. 'Colt' is a trademarked, protected nursery product. Both 'MF12/1' and 'Colt' are best used as rootstocks on which buds are grafted close to the ground. Any difference in growth of thickness between cultivar and stock will hardly show on such low-grafted trees. No reports are known to us of an incompatibility between stock of Prunus avium, 'MF12/1', or 'Colt' and any cultivars of P. serrulata. To grow a field of garden cherries for the trade, it is advisable to start with virus-free stock and virus-free cultivar material. For the commercial nursery it is of utmost importance to keep the nursery virus-free. Therefore the soil should be healthy or even sanitized and must be free from nematodes such as Xiphinema and Longidorus, which have proved to transmit virus diseases. Budding, Chip-Budding, and Grafting The methods of setting a cultivar on a rootstock are in a more precise sense treated in the following paragraphs. Budding of cherries is only done in Europe; chip-budding and grafting are practiced worldwide.