Rebutia minuscula
Rebutia minuscula is a species of cactus from South America found in northern Argentina and Bolivia. It is the type species of the genus Rebutia. As its synonym Rebutia senilis it has gained the Royal Horticultural Society’s Award of Garden Merit. Its cultivars 'Krainziana', 'Marsoneri' and 'Violaciflora' are also listed as having gained the Award of Garden Merit. The status of the species of Rebutia is currently uncertain; indeed the genus as defined by Anderson (2001) has been shown to be polyphyletic. Anderson describes R. minuscula as consisting of globe-shaped stems with a diameter of up to , forming large clusters. The stem has 16–20 ribs with small but distinct tubercles ("bumps"). Each areole produces 25–30 fine whitish spines,  long. As in other species of Rebutia, the flowers are not produced at the top of the stem, but from around the base. They are red, up to  long. Other authorities include synonyms such as R.marsoneri, with yellow to orange flowers, in R. minuscula, giving the species a much broader range of flower colour. Subtaxa
The following varieties are accepted:
Rebutia minuscula var. minuscula
Rebutia minuscula var. wessneriana (Bewer.) Eb.Scholz

Synonyms 
Since the early 1990s, more than two dozen additional Rebutia species, previously considered independent, have been included in this species. These include the following:
 Rebutia chrysacantha
 Rebutia iseliniana
 Rebutia senilis
 Rebutia stuemeriana
 Rebutia marsonerii
 Rebutia krainziana
 Rebutia calliantha
 Rebutia kesselringiana
 Rebutia ionantha
 Rebutia kariusiana
 Rebutia grandiflora
 Rebutia knuthiana
 Rebutia carminea
 Rebutia violaciflora
 Rebutia wessneriana
 Rebutia xanthocarpa

References

minuscula
Cacti of South America
Endemic flora of Argentina