Rebutia pygmaea

[Les.Needham]

It seems to me that it would be a good idea to take cultivational experience into account when creating a genus. This is of course non-quantifiable and therefore anathema to a taxonomist, but I think it has been applied in the past though not overtly. The difference in rate of growth under similar conditions; healthiness of otherwise under the same conditions; willingness to germinate without some extreme measure. These seem to be factors which are generally ignored. Looking,for example at Sulcorebutia vs Rebutia, would you not say that they require different treatments in cultivation and that they have different rates of growth? Look at that mixed bag that Hunt chooses to call Sclerocactus. The few plants of Echinomastus that I have experience of seemed easy to grow, initially, but had a propensity to die suddenly for no apparent reason. Ansistrocactus scheerii had no problems at all; grow it like a Thelocactus or even a Fero. Toumeya is a peach. I had a tray full of the things on their own roots. One otherwise uneventful morning I got up to find that every one of them was dead (all of them were on their roots for about the same length of time - 12 months - not all of them were of the same age). Differences like this occur in this "Schlerocactus". Such differences are of more significance than the elongation of an areole or similar morphalogical features. It is not a properly considered genus. It is Hunts hold-all to avoid creating more genera.

[DaveW]

Whose growing conditions would you use as a yardstick? What is easy to cultivate for one person in the microclimate of their greenhouse, or area if grown outdoors in warmer climate, can be difficult for another cultivator. What may be hard for Kew to grow may come up like weeds in a botanical garden in another country.

Some Mammillaria's are easy to grow, some difficult, but exactly which species may vary collector to collector. Difficulty often depends on the microclimate they are grown in, so whose cultivation would be used to decide speciation?

Not all plants formally classed under Rebutia are easy to grow either.

http://www.cactus-art.biz/schede/REBUTI ... jianii.htm

How many plants of a proposed species would you require to be cultivated before they produced the meaningful answer you seek? Plants vary individual to individual and if you set a pan of wild collected seed some will grow better than others, surely they would not constitute different species?

Plants of the same species also vary in habitat, as the following link by Ralph Martin shows. Unfortunately what we often cultivate is what an old friend of mine used to call "a British standard species". A plant now often atypical of the average plant found in the wild because it had been artificially selected for its long maybe colourful spines, or a particular flower colour, and then extensively propagated (often hybridised) to enhance these features so it now bears only a passing resemblance to habitat material. In other words it has just become a nurserymans house plant rather than a botanical species. But some collectors still think if an original description based solely on one original type collection states it had spines 5mm long and 5 spines per areole if they receive habitat seed from the type locality that produces plants with spines 10mm long and say seven spines per areole it automatically cannot be the correct species.

http://ralph.cs.cf.ac.uk/papers/Others/Whatsinaname.pdf

There is an article on Aylostera that may interest you in issue 5 of the free to download Cactus Explorer (page 41).

http://www.cactusexplorers.org.uk/journal1.htm

I think we should stick to describing species based on their habitat variation without complicating it with factors like ease of cultivation etc. Classification was invented by botanists for botanists so they could put plants in their own pigeonholes, they never intended it for we amateurs.

I am afraid your friend Herr Backeberg once described as a new species a plant he only saw passing by his train window on a trip in habitat without ever having handled or collected it first hand (a Soehrensia I think). So I would not place too much reliance on his concept of species, or even genera. That is not to say he did not discover some good species though.

DaveW

[vbueno]

I'm not a botanist or desire.
And I very much like to express our opinion of biology collectors.
On the other hand I have to use a standard cactus names among the community of collectors. And that standard is preferable to put the scientific community.
And I am grateful to Linnaeus. Every day I remember him when I see Cynara cardunculus plants that grow near my house.
I am a psychologist and I very much like everyone opine about psychology, but to classify psychological disorders use the names of the scientific community, not people use custom.
On the other hand, I'm interested especially hybrids get cactus. So I look over their similarities than their differences.
And I love all forms and varieties of Rebutia pygmaea
http://good-rebutia.blogspot.com.es/sea ... date=false
Vicent