Many such arrangements of boxes, perforated cans, pieces of tile, etc., have been proposed during the last fifty years in California for accomplishing the purposes which are mentioned in your letter, and all such devices have been abandoned as undesirable. They may bring the water to bear upon a lower level as intended, but the free access of air and the fact that, with their use, proper stirring of the soil is neglected renders them undesirable. The best way to water young trees singly is to make a trench around tree, but not allowing the water to touch the bark, applying the water and then thoroughly hoe when the surface soil comes into proper condition. Young trees treated in this way, with the surface always in good condition, do not require much water. The amount depends, of course, upon whether the soil is naturally porous or retentive. Underground Irrigation. How extensively used and with what results is the underground tile system for irrigation used, and what especial character of soil is it best suited for? Not extensively at all; in fact, if there is an acre of it which has been for three years in continuous and successful operation, it has escaped us. After forty years of trial of different systems, none has demonstrated value enough to warrant its use. Theoretically, they are excellent; in practice they are defective. Surface application in different ways, according to the nature of the soil, accompanied with thorough cultivation, is the only thing that at the present time promises satisfactory results, except that where the land suits it, irrigation by underflow from ditches on higher elevations is being successfully used on small areas in the foothills. For gardens the most promising arrangement seems to be a laying of drain tiles rather near the surface, which shall be taken up each year, cleaned of silt and plant roots, and relaid along the rows before planting; but this calls for too much labor, except perhaps for amateur gardeners. The kind of soil best suited to such a system is a medium loam which will distribute water sufficiently to avoid saturation and air-exclusion. Both a heavy soil which does this, and a coarse sandy loam which takes water down out of reach of shallow-rooting plants too rapidly and lacks capillarity to draw it up again, are ill adapted to underground distribution. Irrigation of Potatoes. Will you kindly tell me when is the proper time to irrigate potatoes, before they bloom or after they bloom, and do they require much water?