The plants are grown from seed, and it is customary, in tropical countries, to sow several crops each season to insure against failure and that collecting may be less interrupted. Plants of the spring sowing flower in July. The pods do not all mature at the same time; this, coupled with the sowing of several crops at intervals of four to six months, makes the work of collecting almost continuous. Before the pods are fully developed they are incised horizontally or vertically with a knife. Generally a special knife with two and three parallel blades is used. The blades of the knife are repeatedly moistened with saliva to prevent the poppy juice from adhering to them. The incisions must not extend through the walls of the capsule, as some of the juice would escape into the interior and be lost. As soon as the incisions are made a milky sap exudes, which gradually thickens, due to the evaporation of moisture, and becomes darker in color. The following day the sticky, now dark-brown juice, is scraped off and smeared on a poppy leaf held in the left hand; more and more juice is added until a goodly sized lump is collected. These sticky, ill-smelling masses of opium are now placed in a shaded place to dry. The entire process of incising and collecting as carried on by the Orientals is exceedingly uncleanly. To the nasty habit of moistening the knife-blade with saliva is supplemented the filth of unwashed hands and the sand and dirt of the poppy leaves, which are added from time to time to form a new support for the juice as it is removed from the knife. In scraping the gum considerable epidermal tissue is also included. Each lump of gum opium contains therefore a mixture of spittle, the filth of dirty hands, poppy leaves, sand, and dust. In addition to that many collectors adulterate the gum opium with a great variety of substances. Dioscorides mentions the fact that even in those remote times adulteration of opium was practiced, such substances as lard, syrup, juice of lactuca, and glaucium being added. Modern collectors and dealers adulterate opium with sand, pebbles, clay, lead, flour, starch, licorice, chicory, gum arabic and other gums, figs, pounded poppy capsules, an excessive quantity of poppy leaves and other leaves, etc. After collecting and drying the peasants carry the gum opium to the market-places, where they are met by the buyers and merchants, who inspect the wares and fix a price very advantageous to themselves.