I heard you can put the seeds in a bag with a banana peel, or apple. The rotting fruit gives off ethylene gas and aparently changes seeds with male sex genes, to female. I guess at that young stage the difference between male and female is small. I've read articles on here where people have put seeds in bags with banana peel 2 weeks before germinating and have resulted in 100% females. Or like mentioned above, stress the plant to hermie and self pollinate. I was curious about this a while back as well (purely from a biologist/science point of view), and from what i read, it seemed like spraying colloidal silver on the plants was the safest, most effective method. There'r many ways to stress a plant to hermie, like using toxic chemicals like giberillic acid or light stress, but colloidal silver is said to work. Also, colloidal silver is safe to ingest, and is sold in health food stores as an immune boost supplement (my dad has some in his vitamin cabinet that he takes when he thinks he's getting sick, so its very safe). Do some reading on C.S. effects on mj and find out more accurately than listening to me. Also the people that used it, sprayed lower branches of plants every day for the first 2 or 3 weeks of flowering. Or just wait 2 weeks for seeds to sit in a bag with rotting banana peel. Read up on that too and decide for yourself which seems best