Keith, are you talking about Gymnocalycium mihanovichii? I assume you don't mean a columnar cactus with a round purple top that has been grafted onto it.
Put your cactus soil in a container about 4 inches deep. Make sure there is excellent drainage. Water the soil. Shake the seeds onto the top of the soil and cover with no more than about 1/8" of soil. Put into a clear plastic bag to keep soil moist and so that you can see the growth. Keep warm (at least 70°). It takes about 1 to 4 weeks for germination depending on conditions. Don't put the container in direct sunlight but do place where there is bright light. Repot after several months.
