There are four characteristics that distinguish Coryphantha from other cacti. Their bodies do not have ribs, just tubercles. The flowers form at the top of the plant (the apex or growing end of the stem). The tip (podarium) of each flowering tubercle has three parts, the spiny areole, the groove and the axil. Without the groove it is not a Coryphantha. The seed coat (or testa) has a net-like pattern