Almond is losing favor as a rootstock for almonds in heavy and poorly drained soils because they appear to be more susceptible than peach to crown rot.

SWEET AND SOUR cherries are grown chiefly on mahaleb, P. mahaleb. Mazzard, P. avium, is preferred in some areas.

The seeds of mahaleb are harvested from seedling orchards grown entirely for seed purposes. New varieties, known as Russian and Turkish mahaleb, have been tested and have proved to be more vigorous and winter hardy and appear very promising.

Mazzard seeds used to be obtained from pollinator trees in western orchards and from wild native trees in the eastern States. Improved strains of the so-called "silver bark" mazzards, imported from Germany by the Geneva branch of the New York Agricultural Experiment Station, appear promising. Because the ring spot, sour cherry yellows, and prune dwarf viruses are seedborne, scientists began work to establish virus-free orchards as sources of seed: Some seed of both rootstocks still are imported from Europe.

MOST OF the apples in the United States formerly were propagated on French crab, a cider apple grown in France. More recently, seedlings of domestic varieties, such as Delicious, Winesap, Jonathan, Rome Beauty, and York, have become widely used.

In places subject to low winter temperatures and sudden drops in temperatures, the practice of double working to produce trees with cold-hardy trunks is increasing. The use of partially incompatible trunk sandwiches interstocks between the variety top and the seedling rootstock to produce dwarf trees has become popular, but most dwarf trees are produced by growing varieties directly on dwarfing stocks, like the East Malling and Malling Merton series. Apples are grown commercially only on apple rootstocks and appear to grow equally well on seedlings of most commercial varieties.

PEARS are grown mostly on domestic Bartlett seedlings. The early pear plantings in the United States were almost entirely on French pear seedlings. Since 1920 or so, most of the pear stock was grown on oriental pear understock from seed brought from Asia. They produced vigorous trees, and were liked in the nursery because of some resistance to fire blight and woolly root aphis and freedom from leaf troubles. The association of hard end and black end of the fruit with oriental rootstock discouraged their use, and no oriental stock is used in the commercial pear orchards of western States.

PEAR DECLINE, a new disorder that has devastated pear orchards in the western States, has been associated with oriental rootstocks and has brought about renewed interest in pear rootstocks.

The Angers quince propagated vegetatively is used as a dwarfing stock for pears, but there is wide variation in behavior of varieties grown directly on quince. Bartlett normally does not do well on quince. In areas where blight is bad, blight-susceptible pears are grown on trees composed of seedling roots, Old Home, or other blight-resistant variety trunks on which the desired varieties have been top-worked. If planted deep, the Old Home often forms roots above the bud union with the original seedling.

The Persian walnut, Juglans regia, is grown mostly on the northern California black walnut, J. hindsii. Regia seedlings, Royal and Paradox hybrids (J. hindsii X J. nigra), and (J. hindsii X regia) have been gaining in popularity because of black line, a disorder in which the bark dies at the bud union on trees of Persian on J. hindsii. Regia and its hybrids appear to be more resistant to the meadow nematodes.

PECANS are grown almost entirely on domestic pecan seedling rootstocks. Seed from scab-resistant varieties with medium-size nuts, such as Curtis and Stuart, are preferred, because the seedlings in the nursery are less affected by scab and make more vigorous trees.

The small, native western nuts produced out of the heavy scab area are apt to be highly susceptible to scab and should be avoided.

TUNG is grown mostly as seedlings directly on their own roots. Seed should be collected as first-generation seed from clonally propagated varieties that have progeny performance records as to production, oil yield, vigor, and cold hardiness. Seedlings of Folsom, Lampton, and LaCrosses come true to the parent type. Lampton is probably the most widely used seed parent.

Filberts are grown from layered cuttings and thus are on their own roots. Trees are mounded and new plants are obtained from the suckers that grow from the base of the tree and root in the mound.

Figs are nearly all grown on their own roots. Cuttings are made of dormant 1 to 3-year-old wood, which is buried until it is well calloused. Then it is planted in the nursery row and later in the orchard. Some varieties have shown greater vigor and nematode resistance and are used as rootstocks for other varieties.

L. C. COCHRAN, Chief, Fruit and Nut Crops Research Branch, Agricultural Research Service, studied horticulture and plant pathology at Purdue and Michigan State Universities. He did research at the University of California before joining the Department of Agriculture in 1941. He has published many papers on the ills of fruit trees, particularly in the field of virus diseases.

W. C. COOPER is plant physiologist in charge of citrus and subtropical plants production investigations, Crops Research Division, Agricultural Research Service, Orlando, Fla. He holds degrees from the University of Maryland and California Institute of Technology. His research field has been with citrus rootstocks and citrus nutrition.

EARLE C. BLODGETT holds a dual position of plant pathologist with the Washington Department of Agriculture and the Washington Agricultural Experiment Station. He holds degrees from the Universities of Idaho and Wisconsin. He has done research work on diseases of fruit trees, with particular reference to diseases of nursery stock.