Mammillaria elongata 'echinaria'

This picture  of young seedlings if asked for plant IF will puzzle almost every cactus collector. Mammillaria elongata is one of the most common cacti in culture, but 'echinaria' form is not so well known. This plant was originally described as M. echinaria, but the only notable difference with M. elongata is the persistent central spines, so taxonomically M. echinaria was downgraded to a merely form.
That does not change that it is very decorative plant, one of the most attractive in the genus.