Seeds are the typical way of reproducing. These cacti will easily grow from seeds and some from cuttings. Seeds can be sown in the spring or summer in well-drained pots of soil for cacti. Sow the seeds thinly on top. Cover them with a bit of fine quartz grit. Moisten and lay a piece of glass across the top. The pots should be set in a warm greenhouse until they start to sprout, after which the glass should be progressively removed so they can receive full light and air. It isn't good to keep the glass over the seedlings. The well developed seedlings can be planted separately in small pots. Cuttings made from pieces of the stem of any size can be detached and laid aside for a few days to allow a protective "skin" to form over the cut. They can then be planted in pots. Place them in a spot where they'll receive sun, and do not water until the soil becomes fairly dry. After a while the soil can be moistened regularly, but never kept constantly saturated.