Preflowers, as opposed to full blown flowers, generally appear after the fourth week of vegetative growth from seed. Check carefully above the fourth node. Please note that preflowers are very small and impossible to differentiate without magnification. A photographer's 10x loupe is handy indeed when examining preflowers.
As the images below demonstrate, the female preflower is pear shaped and produces a pair of pistils. Frequently, the female preflowers do not show pistils until well after the preflowers have emerged. Thus, don't yank a plant because it has no pistils.Pistillate preflowers are located at the node between the stipule and emerging branch.
The male preflower and flower may be described as a "ball on a stick." Frequently, a male plant will develop mature staminate flowers after prolonged periods of vegetative growth. These appear in clusters around the nodes.
The following image shows a male plant in early flowering. Staminate flowers are located at the node between
the stipule and emerging branch. Note the clusters of flowers.