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Plant of the Month
This beautiful, but rather infrequently encountered, species comes from Jujuy, in Northern Argentina. It is quite easy to grow, using 'standard cactus treatment', and flowers reliably in spring, around May. It comes from an altitude of 4000m, so will survive in an unheated greenhouse in winter if kept dry. It is perhaps a little slower growing than some of the larger Aylosteras but most forms eventually clump up, although some of the larger-bodied forms have a greater tendency to remain solitary.
This species, until quite recently, would have been called a Rebutia, either Rebutia fischeriana or, in earlier publications, Rebutia euanthema v. tilcarensis. For a long time various plants that earlier authors had called Rebutia, Mediolobivia and Aylostera were all brought together into the genus Rebutia. However, recent DNA studies have shown that this is a case of convergent evolution, i.e. rather distantly related plants evolving under similar conditions to look very similar. We now know that Rebutias, in the original narrow sense, are only distantly related to Aylostera and Mediolobiva. However, the latter two are very closely related, and should now all be called Aylostera (as that is the older of the two names). So, although this plant was first described as a Rebutia, it is now properly recognised as Aylostera fischeriana.
So, enough of taxonomy. Let's look at the plant itself. As Figures 1-5 show, it is quite a variable species, so it is unsurprising that some forms have also been considered to be close to, or even belong to, Rebutia einsteinii. The heads can vary from very small (small-finger-tip size) to medium (stout-thumb size), while flower colour can vary from pink to orange to red. Generally, the spines are fairly dense, although they can be quite short on some forms and longer on others. However, a careful examination shows they are all closely related, with two characteristic features. First, the stamens have dark filaments (these are the stalks with the pollen at their tips), unlike most Aylosteras which have pale coloured filaments. Second, the spines are all radial – there are no central spines. Furthermore, the spines lie close to the plant body, but are not quite pressed flat to it. Instead they radiate and are slightly angled away from the body, in a way that is hard to precisely express in words, but if you look enough at these plants and other Aylosteras, you can come to see it is distinctive.
One last point: what do the letters and numbers after the names signify? These are field numbers. Plants with the same field number should all be propagated (either by cuttings, or seed) from the same original collection. The field number indicates who made this collection, and acts as a reference to data about it. For example, WR refers to Walter Rausch, while 751 is a serial number – his first collection was WR1, and so on. You can look up field numbers in Ralph Martin's Field Number Database.
Figure 1 Aylostera fischeriana WR751
Figure 2 Aylostera fischeriana MN188
Figure 3 Aylostera fischeriana MN171a
Figure 4 Aylostera fischeriana RH1310/2
Figure 5 Aylostera fischeriana MN163
Text: Ralph Martin. Photos: Xiaoqing Li
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