Xerophyte

Flowers

Typical of the series Longiflorae, crocus-like, funnelform, pink, unusually long-stemmed for a Mammillaria. Larger than the plant body itself, at least with plants on their own roots.

Spines

Pectinate.

Fruits

Cryptocarpic (In a cavity in the plant body). Mammillaria bertholdiiSN|9674]]SN|32468]] is one of the few species of cactus with cryptocarpic fruits. That is, the fruit and seeds are produced and retained inside the stem of the plant. After the flower is finished and dropped off, the stem closes over the fruit and the fruit/seed gradually ripens within. The following years the fruit may remain within the body at the axil, or may protrude a bit. A thin membrane will be above the part where ripe seed can emerge. As the plant swells with the new growing season, the membrane fractures, and some seed from the past years can little by little drop down and germinate in the close proximity, forming small colonies. But usually the seeds remain within the plant body for several years or for the whole life cycle of the plant, and frequently they will be released only at the death of the plant after the disintegration of the old stem.It is possible to collect fruit and seeds only by means of a thin pointed forceps. The seeds' vitality lasts for many years and moreover seeds contain inhibitors that preserve them from premature germination. Generally fresh seeds won’t germinate very well, only old seeds do. The complete germination of this kind of seed may take several years (Some will sprout unexpectedly after 5 or 8 years!). Because of the above peculiarity, seeds and plants of cryptocarp Mammillaria (Series Longiflorae) are seldom available from commercial sources.