I seriously doubt it will grow leaves unless it has light. Then the light will eliminate moisture, therefore leaving you to maybe losing your plant.

Gently plant it in some fresh soil!!

I have a few Kumquat sprouts. As countycarolyn said, plant it in some soil. I use styrofoam coffee cups with a punched hole to start.

Be advised that Kumquats do not grow well on their own roots, so you might want to graft it eventually.

as soon as that seed even cracks(you dont need to see root)
it should be planted in soil, as a rule of thumb, twice the seeds thickness deep.

if you leave it in the towel, the root will grow longer than it should be, and be prone to snapping.

It will most certainly produce leaves without light. Cotyledons exist to some level before the seed even cracks. Without light to the cotys the roots will cease to grow, and the plant will die.

I planted my seeds in a clear hard plastic food container and placed them in the window sill. After they got a good start and had a couple of leaves I planted them in individual pots and lifted the plant so that 3/8 inch of the root was above the soil line. The ones I planted below the soil line die from trunk rot. Take the standard procedure for growing citrus.

Have your trees turn out well. Could you post pictures. See my picture below.

{{gwi:31428}}
Meiwa kumquat tree grown from seed.

Here is a link that might be useful: https://plus.google.com/photos/111099372377958308731/albums/profile?banner=pwa