It has to do with what the preflowers look like. Before it flowers, it shows evidence of sex. Males have little sacks that look like balls before they flower, females have pistils (little white hairs) that turn into bud sites. I think there is a faq https://www.rollitup.org/view.php?pg=faq which has all sorts of useful informationnice thanks everyone, to go along with the male/female plants, i was reading another thread and somebody posted pictures about early signs of a male, in those pictures what exactly are people looking at? What gives you a sign that a plant could possibly be a male or a female other than the fact that it buds.