Xerophyte

Habit

Solitary or clustering.

Seeds

Black.

Description

Mammillaria luethyiSN|11876]]SN|11876]] is a very tiny plant, but by far one of the most spectacular members of its genus, distinctive when not in flower because of the 'spination' (if it can be called that!) at the tips of the tubercles, and even more magnificent in flower. It is solitary or branching in several stems, mostly beneath the ground. This species is the most sought after cactus by collectors because of its rarity and unusual spines.

Roots

Fleshy tap root, largely exceeding the dimension of the tiny stems.

Tubercles

Dense, erect, slender, cylindrical. The axil is slightly bristly.

Cryptocarpic Fruit

Mammillaria luethyiSN|11876]]SN|11876]] 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 cryptocarpic Mammillarias are seldom available from commercial sources.

Seasonal Growth and Contraction

In the wild these plants contract considerably during the dry season, sometimes pulling down completely under the soil level, and frequently the flowers push up through the dirt from the underground cactus body. In fact, even though these plants show a good amount of new growth each year (at least 1 or 2 cm), they hardly get any larger, and their dimensions remain unvaried year after year, as the individual stems tend to contract at the base. The new growth produced during the vegetative season compacts considerably and retracts sometime, pulling the plant down completely under the soil in the hottest months of summer and coldest months of winter.It should be noted that "when specimens are in this withdrawn state, it becomes almost impossible to find them in their natural state, even though their exact locality is known"

Flowers

Large, 15-25 cm wide and long, rich magenta with a white throat.

Spines

Short, minuscule, as many as 80, soft and white, not prickly, in several series, erect to radiating, forming a dense, flattened cluster 1-2 mm in diameter

Stem

1.5 cm in diameter (Up to 4 cm in cultivation), flattened sub-globose, very dark-green almost black.

Fruits

4 to 5 mm in diameter, sunken in the stem, globose, yellow-green to reddish-green.