But study of the ruined vines revealed the cause of trouble. No one could devise any means of killing an insect enemy that works underground. But the wild American vines, that showed ability to resist the attacks of the phylloxera, were taken to Europe and planted. Then the varieties that had been destroyed were grafted on the hardy roots. Thus the immune grape acted as nurse and guar dian to the tender wine grapes, and the enemy was defeated. Rugged native species saved the high-bred varieties from ruin.
Wines are made by crushing the grapes and let ting the juice ferment. The skins may be fer mented in the juice and thus make red wines, that take their color from the pigment under the skin. Juice alone is used in making white wines. The acid in grapes gives the wine-keeping qualities. The sugar produces alcohol. During fermenta tion, a grayish or reddish crust forms in the wine vat. This crystalline substance is "argol." Refined, by dissolving and filtering processes, it becomes "cream of tartar," used in medicine, effervescent drinks, and in baking powders.
After being drawn from vats into barrels, the wines are kept for some years to ripen, if the best qualities are being made. The older the wine, the better it becomes.
Raisin-culture centres in Fresno County, Califor nia, where the fruit of certain fleshy, sweet vari eties are dried in the sun, on large trays. Only regions of continuous sunshine can make raisins.
Valencia and Malaga, cities in Spain, are cen tres of great raisin-districts in Europe. The finest grades are produced by partially cutting the stem of each fine cluster, and then cutting away of all leaves, so that the sun hastens the drying, and the sap supply is partially cut off. The more usual method is to cut the bunches and lay them on trays in the sun.
Persia and neighboring countries produce quanti ties of raisins for home use and for European markets. The Zante currants and Sultana seed less raisins are both made of small sweet grapes of Greece and Asia minor.