The flowers of Cannabis sativa are unisexual and plants are most often either male or female.[3] It is a short-day flowering plant, with staminate (male) plants usually taller and less robust than pistillate (female or male) plants.[4][5] The flowers of the female plant are arranged in racemes and can produce hundreds of seeds. Male plants shed their pollen and die several weeks prior to seed ripening on the female plants. Under typical conditions with a light period of 12 to 14 hours, both sexes are produced in equal numbers because of heritable X and Y chromosomes.[6] Although genetic factors dispose a plant to become male or female, environmental factors including the diurnal light cycle can alter sexual expression.[7] Naturally occurring monoecious plants, with both male and female parts, are either sterile or fertile;[clarification needed] but artificially induced “hermaphrodites” can have fully functional reproductive organs.[8] “Feminized” seed sold by many commercial seed suppliers are derived from artificially “hermaphroditic” females that lack the male gene, or by treating the plants with hormones or silver thiosulfate.