There is currently still no scientifically sound explanation as to the origin of the so-called "fairy circles" in the Namib. An in situ experiment was conducted in the NamibRand Nature Reserve to test the latest hypothesis that the circles are the result of a semi-volatile gas that inhibits plant growth. Stipagrostis ciliata grass plants were planted in containers filled with soil from the circle or from outside the circle. Some containers were sealed at the bottom, to prevent any gases from entering from below, while others were left open. Containers were placed both inside the circle as well as outside the circle. The origin of the soil, i.e. whether it came from inside or outside the circles, did not affect the performance of the plants when they were growing in the same position and container type. All plants growing outside the circle, irrespective of the origin of the soil or the container type, performed better than those growing inside the circle. It is concluded that there is a factor inhibiting plant growth in the circle and that this factor could possibly be a semi-volatile gas, because growth was more negatively affected in the open containers than in the sealed containers. Keywords: Desert, Fairy circle, Namib, Termites.