WATERCRESS is in constant demand the year round in the markets of all large cities, so it is a salable crop which should especially appeal to the commuter class of farmers, as it must be freshly gathered to be at its best, and naturally cannot be shipped long distances to market, which is perhaps the principal reason for its being such a profitable crop. In France and England, watercress farms are quite numerous, especially in the vicinity of Paris and London; but in this country it is only just beginning to be cultivated to any great exte............