Sulcorebutia, food for taxonomists?

Sulcorebutia, food for taxonomists?
Summary
Many cactus lovers seem to have an opinion about the nomenclature of their plants. But do
they really know the right name? Who will determine this and in particular, how is it done?
We haven’t heard the last word on this subject.
Creation of the image
My cactus hobby was scarcely born, when I met Karel. He presented himself as a very
experienced collector. He invited me emphatically to visit him. And not to hesitate in asking
any question. As I was eager to learn, I accepted the invitation gladly. Within a week I had
entered his sanctum. It was indeed a paradise. Many plants were in bloom. In every flowerpot
there was a label with a name on it. This was quite a different experience to “120 cacti in
colour”. 1
Shortly before the visit somebody asked me, if I already had the “hand of the negro”
(Maihuenopsis clavarioides). I hadn’t a clue, but Karel showed me the plant immediately. He
was definitely an expert. “But”, he said, “my great love are the jonias.” These I also knew
nothing of but Karel showed me them and he was entranced as he described the beautiful
flowers. At that very moment Jaap and Gijs dropped in by chance.
“These are not jonias”, Jaap corrected. “These are lobivias. To be more precise Lobivia
jajoiana from Bolivia.” Karel looked bewildered but kept silent but Gijs raised his eyebrows:
“Actually they are echinopsis from Argentina.” As if stung by a wasp Jaap turned. “They do
come for sure from Bolivia. After all you can derive this from the name. And I heard it
personally from Backeberg. He cannot be wrong, as he found them himself. You say
Echinopsis? You mean Echinocactus? But these plants are lobivias and there is an end to it!”
I didn’t understand much of it. Had Jaap really had contact with the famous Backeberg ? On
the other hand Gijs didn’t look stupid. I chose to keep silent as I didn’t want to be thought a
dummy. A few minutes later the guests left. Karel muttered to me in offended tones “This
Jaap, he must always know better! The only thing that really matters is that you understand
me. Isn’t that right?”
Not lobivias, but sulcorebutias took up all my attention during the next years. But during my
search for possible correct names I have heard such conversations over and over again.
Apparently we cactus lovers feel a deep satisfaction in such talks, in which expertise is not
really required. I believe that German-speaking people use the word “Bierernst” in such cases.
I was struck by the fact that many statements made no reference to supporting information.
Observations were hardly done, but this was no obstacle to having a firm opinion.
For the record I should say that names used in this article correspond to what hobbyists on the
continent use to say. This does not mean
that the original authors will always still
support these names. Therefore author-
citations are omitted in this paper.
Rebutia
A small plant with the name Echinopsis
minuscula was brought onto the market
by Pierre Rebut. It probably came
originally from Argentina. Later on such
1 A booklet for beginners
Fig. 1 Rebutia minuscula

plants were indeed found in the province of Tucuman.
In 1895 the genus Rebutia was defined by K. Schumann. (Fig 1) Schumann had observed that
the new plant did not bloom from the areole, so it could not be an echinopsis. The plant itself
resembled an echinocactus or malacocarpus, but as the flower originated from outside the
areole, it had to be related to Mamillaria “without any doubt”. The shape of the corolla and
the pericarp however prevented classifying it here. Some years later Schumann withdrew
Rebutia.
28 years later on Spegazzini (1923) defined the genus Aylostera. The decisive feature was a
partial fusion of the style and the tube. Using this characteristic one could clearly distinguish
Aylostera from Rebutia. (Fig 2 and Fig 3)
Fig. 2 Flowersection Rebutia minuscula Fig. 3 Flowersection Aylostera schatzliana JK423
Have the observations of Schumann been checked? I suppose so. Though I was never able to
confirm that Rebutia did not bloom from the areole. But I have heard amateurs discussing
seriously about pistils which had grown together to the tube opposite free pistils.
Berger (1929) did not mention a genus Aylostera. He recognized only one genus Rebutia. He
wrote: “Small pants, roughly globular, reminiscent of mamillaria, with tubercles in spiral rows
and small spines. Flowers from the older areoles, often originating close to the base, small,
funnel-shaped, with slender tube, open by day. These small plants from the mountains are
not to be classified in Echinocactus nor in Echinopsis.”
I have some problems with this statement. Schumann used the observation that the plant did
not bloom from the areole to distinguish the genus. The same characteristic was denied by
Berger. What did he observe instead to be still able to recognize a genus Rebutia,
distinguishable from other genera? We never will know.
Berger mentioned 6 species: Rebutia minuscula, R. deminuta, R. pseudominuscula, R.
pygmaea, R. fiebrigii and R. steinmannii, of these the first four species came from Argentina
and the others from Bolivia.
Does the characteristic, that pistil and tube are partially grown together, make any sense? One
taxonomist will find it important, the other will dismiss it. It was Ritters opinion (1980), that
the fusion hardly had taxonomical meaning, as it would have developed simultaneously in
different separated lines.
Often the characteristic is ignored. How would early taxonomists have decided whether a
plant belonged to Rebutia or not? I suspect that plants have been thought to be related after a
rough observation without a real check. Is this strange? No, because such things still happen.
It would be really strange, if one used a formal checklist of characteristics for every new plant
to decide to what genus it belongs. The rough and ready approach is a natural way of acting,
but of course it contains the risk of overlooking a significant characteristic.

In the same way relationship between plants
will not only be accepted, but denied as well.
Many people do accept Rebutia minuscula and
Aylostera pseudominuscula to belong to the
same genus. But who will for example expect
a closer relationship between Rebutia
minuscula of only a few centimetres diameter
and height and a 5 meters high Browningia
candelaris? (Fig. 4) Nobody, don’t you think?
More about this later.
During the winter of 1929-1930 the plant
collector José Steinbach sent Werdermann a
plant, which “probably had been discovered
in the wider surroundings of Cochabamba
Fig. 4 Browningia candelaris (Foto: Craig Howe,
(http://cactiguide.com/cactus)
(Bolivia) at an altitude of 2500 m”. Unfortunately Steinbach died shortly afterwards.
Werdermann identified the plant as “doubtless” being related to Echinocactus minusculus.
“Schumann had defined, based on its special flowering characteristics, the genus Rebutia,
which he withdrew later on, and classified this plant as Echinopsis.” But Werdermann himself
argued to reintroduce the genus Rebutia for this “well characterized” group.
It may be just me, but I have no idea what Werdermann meant with “well characterized”. Did
he possibly understand Rebutia in the same way as Berger?
Werdermann (1931) described the “interesting” plant, which strongly resembled Lobivia
boliviensis qua habitus, but nevertheless was called Rebutia steinbachii based upon one single
flower. A second opinion was impossible, as the plant had died when the publication was
made.
By the way, to my mind a plant can be called interesting if it is little known and in the mean
time is or will be desirable. It must be more than just a study-object. The possession of
interesting plants works as a lure for collectors by the way. Thinking back, I guess, that in this
sense Karel did not have many interesting plants. Who indeed wants a “jonia”?
Weingartia
As far as I know all authors mentioned above were professional botanists. But amateurs also
made their contributions heard. Very well known was Curt Backeberg. According to
Wikipedia he met the Czech plant collector Alberto Vojtěch Frič by chance in 1927. His
stories stimulated a desire for adventure in Backeberg who decided to import cacti himself.
He was so strongly fascinated by these plants that he published a lot, for example the standard
work of six parts „Die Cactaceae“.
Fig. 5 Weingartia fidana Fig. 6 Weingartia neumanniana

minuscula? Albert Hofman (personal statement) assumes that the first description of the
species fidaiana (fidana Hunt 2006) has to be taken as a first description of the genus also.
Well, I have seen quite some cacti with this label, but with many of them I really had doubts
that these were the plants meant by Backeberg. Are experts more flexible than me? Or is there
insufficient quality of reference data (incomplete, inaccurate), as a result of which
classifications are also unreliable.
Another genus Spegazzinia already existed at the time. Therefore Werdermann changed the
name of the genus into Weingartia (1937) without supplying extra information. Later on
Echinocactus cummingii, which had been described already in 1849, was also classified in
this genus. The result of this remarkable sequence of events was nevertheless correct. Not
only was the genus Weingartia poorly defined by the summary description of Backeberg, the
plant description also was not clear, as the name had been used twice, for completely different
plants, which had died long ago.
Boom (1962) dedicated a very worthwhile article to the correct name of the plant. He ended
his account with the remark “Look at what the consequences may be if the international Rules
for Botanical Nomenclature are not employed in the right way; it is definitely necessary, that
everybody, who is occupied with the taxonomy of cacti (and of course of all other plants)
acquaint themselves with the proper use of these rules. Especially in the case of cacti much
incompetent work has been done in this area.“ Then a list of names followed. In case of
ambiguous names was added „quoad descr.“.
Echinocactus cumingii Salm Cat. Hort. Dyck. 1849, 174 (1850) non Hopffer, Allg. Gartenz.
11, 225 (1843)
Lobivia cumingii (Hopff.) Br. & R., The Cact., 5, (1922). quoad descr.
Oroya cumingii Kreuz., Syst., 1935
Spegazzinia cumingii (Hopff.) Back., Kakt. ABC, 298 (1935), quoad descr.
Weingartia cumingii (Hopff.) Werd. ex van Oosten in Succ. 21, 129 (1939), quoad descr.
Weingartia neocumingii Back. in Kakt. u.a. Sukk., 1, 2 (1950).
Fig. 6 Weingartia neumanniana
Gymnantha cumingii (Hopff.) Ito, Expl. Diagr. 53, 1957, quoad descr.
Gymnocalycium neocumingii (Back.) Hutch. in Cact. & Succ. J. (U.S.), 29, 1957
Gymnocalycium cumingii (Br. & R.) Hutch. in Nat. Cact. & Succ J., 14, 1959.
I can imagine that not only the interested amateur will be lost here, the professional
taxonomist will also perhaps do a double-take. How could the name of a species be connected
to different genera so often in only 35 years? Searching for explanations, one is reminded of
the speed with which Jaap solved taxonomical problems.
Personally I would guess that the poor quality of information is the cause of this chaos.
Sulcorebutia
Backeberg defined the genus Sulcorebutia (1951). Here is an attempt to interpret the Latin
text: „Plants caespitose, with rather small offsets, ribs tuberculous; tubercles lobivoid,
axeshaped (!), with crack (!); flower funnel form, originating from the circle round expanded
crack, with the colour of the morning sun, with scales, hairless (!) fruit still unknown –
Bolivia, near Colomi (Cochabamba) in an altitude of 3400m (Cardenas). Typus: Rebutia
Steinbachii Werd.”
The characters followed by “(!)” will have been the main criteria. It is nice to conclude, that
this text differs from the one in “Die Cactaceae” (1959).
Werdermann described the colour of the flower to be red, Backeberg mentioned “the colour of
the morning sun” like the one of Rebutia violaciflora. (Fig. 7) Previously I had heard the
explanation, that some taxonomists were rather flexible in their interpretation of the colour
red. Later on Pip Smart told me, that Martin Cárdenas from Cochabamba had looked for years

for a plant like the one of Werdermann,
with positively real red flowers. He never
found one.
Obviously his quest brought him to the area
east of Cochabamba. Backeberg got his
plants from Cárdenas. It seems plausible,
that the type-plant defining the genus
comes from a population different to the
one described by Backeberg. Is this really
important?
Because herbarium material of the typeplant
of Werdermann no longer existed, in
1999 a neotype was deposited in the
herbarium of the Städtische
Fig. 7 Sulcorebutia steinbachii JK 94
Sukkulentensammlung in Zürich. This suggests it should be a plant from the original
population. Would this plant completely correspond with the description of Werdermann?
David Hunt (2006) explained: “The type (which does not have to be an average or ‘typical’
specimen of the species or other taxon concerned) gives the botanist an absolutely fixed point
of reference from which to judge whether other specimens to which the name has been
applied are correctly identified or not.” Then the neotype was superfluous, if it was identified,
based on the plant of Werdermann, to
belong to the same species. However if the
identification was different, the deposit
would lead to a paradox.
To Backeberg the crack (sulco) at the upper
side of the tubercle was a distinguishing
characteristic of the genus, therefore the
name Sulcorebutia. Moreover he mentioned
the lobivoid appearance of the plant and the
hairless flower. The totally free pistel was
mentioned in the English language
comment. (Fig. 8)
Although Cárdenas sent Backeberg a
couple of plants, he rejected this genus.
There was a rumour that he objected in the first place to the amateurish procedure of
Fig. 8. Flowersection Sulcorebutia steinbachii G123
Backeberg. Anyway, he rejected Sulcorebutia and described for example Rebutia arenacea
and R. glomeriseta in 1951, R. tiraquensis, R. totorensis and Aylostera Krugerii in 1957 and
even Weingartia torotorensis in 1971, all of which were recombined to Sulcorebutia. I never
understood why Cárdenas believed to recognize in this plant an aylostera (with fused pistil
and scales on the tube covered by hairs).
John Donald (1971) made a stand against the opinion of Cárdenas. First he mentioned that
deliberate hybridization between Sulcorebutia and Rebutia had brought no descendants. One
can pollinate Sulcorebutia and Lobivia with Chamaecereus, but not with Rebutia. Also one
can pollinate Weingartia and Sulcorebutia with each others, but again not with Rebutia. Also
hybridization between Rebutia and Lobivia is not possible.
Cárdenas had criticized the European taxonomists because of the lack of field experience with
Rebutia, as a result of which they were not in a position to develop a proper classification.
Such remarks are rather familiar to me in circles of current day specialists. Donald however
had observed hundreds of plants transported directly from their natural surroundings, so he
had a right to speak. In his opinion the separations between species was blurred and he

ecognized clines, for example Sulcorebutia candiae, S. menesesii, and S. xanthoantha and
Sulcorebutia kruegeri, S. arenacea, S. caineana and S. breviflora (brachyantha).
At last Donald compared sulcorebutias, rebutias, weingartias and lobivias with each others
based on 9 main characteristics, divided into 30 sub characteristics. The presence of these sub
characteristics was measured. It resulted in the following table:
L 15 10 10 1
W 10 15 13 4
S 10 13 15 4
R 1 4 4 15
L W S R
The main characteristics were (i) structure of the rib, (ii) tubercle, (iii) position of the areole,
(iv) structure of the areole, (v) appearance of the flower, (vi) structure of the receptacle, (vii)
insertion of the filaments, (viii) fruit and (ix) seed.
I’m afraid I do not understand this explanation of Donald very well.
Fig. 9. Cladogram according to Buxbaum

Franz Buxbaum (1967) did recognize the genus Sulcorebutia. He believed he was able to map
the connections of taxonomical units as determined by ancestry. Of course these units had to
be monophyletic. He intended that a group of taxonomical units should have a common
ancestor, from which all the members of subgroups - but no other groups - are descended.
Buxbaum compiled the following clad gram – in this case a phylogenetic tree. (Fig. 9)
Shifting insight
It is not clear to me how Ritter recognized that for example Aylostera Krugerii was a
sulcorebutia, if he only used the characteristics of the genus Sulcorebutia mentioned by
Backeberg. Maybe he did something like this: B looks like A, C looks like B, D looks like C,
and so D looks like A? Ergo D is related to A? Donald also accepted a considerable list of
sulcorebutias, doubtless by a process of shifting insight. This led automatically to an
extension of interpretation, which was followed by an amendment to the genus (1972). In this
the crack on the tubercle, what gave the genus its name, was still mentioned.
Fred H. Brandt (1977) surprised friend and foe alike by the joining of Weingartia and
Sulcorebutia. He wrote: “As a result of observations spanning many years as well as
investigations of the plants and seeds of these two genera I have come to the conclusion that
these genera are one closed unit and thus have to be joined.“ Consequently all sulcorebutias
were recombined.
It is a pity that I could not recover details of his observations. Nor do I know what he
investigated. When I was introduced shortly afterwards to well-known sulk-specialists I was
pressed emphatically to forget Brandt. Had he committed a heresy? Inquiry brought no more
than a recurrence of the statement.
Donald and Brederoo studied for a
considerable time to decide if or how to
separate the genera. It was not very easy to
obtain an unambiguous judgement.
Perhaps one had to think of three strongly
related groups: (I) the group of the
southern weingartias with Weingartia
fidaiana as a species of reference, (ii) the
group of the northern weingartias W.
neocumingii as a species of reference (Fig.
10) and (iii) the group of the sulcorebutias
with Sulcorebutia steinbachii as a species
of reference. Actually I did not find any
clear motivations for these suggestions.
Fig. 10. Weingartia neocumingii HS 93
By the way, according to Donald Weingartia neumanniana was found in the area of the
Bolivian-Argentinian border, though Backeberg himself stated the area near Humahuaca, 125
km more southward.
Friedrich Ritter (1980) concluded that the observation of Backeberg concerning the tubercle
was based on an illusion. There was no crack at all, only a fold. This phenomenon was found
in other genera as well, for example in Weingartia. But Ritter did recognize the genus
Sulcorebutia because “the short, light edged scales of the flower are not these of Rebutia“.
Moreover he had observed, that the areoles (?) on the flowers of Rebutia (as far they were not
hairless) except wool, almost always bear several to many bristles. Ritter believed Rebutia to
be a genus on its own, to which also Aylostera with its hairy scales belonged. In spite of this
remark I cannot build on the considerations of Ritter. Nevertheless they were good enough for
a series of recombinations, like Sulcorebutia arenacea, krugerii, tiraquensis, totorensis,
which obviously were accepted by everybody. Of course it was annoying, that this seemed to

e overruled by the activities of Brandt. Were the arguments of Ritter more convincing?
Fortunately Nol Bredero and John Donald (1981) were able to make the final pronouncement.
They wrote enthusiastically: „Ein Problem ist gelöst!“ Brederoo had discovered that in case of
sulcorebutias, tiny hairs are found behind the scales on the pericarp, which never occur in
weingartias. The consequence was a recombining of Weingartia purpurea and torotorensis to
Sulcorebutia. The sulco-collectors were satisfied because now it had been concluded
unambiguously, that Brandt was wrong.
I was so naive as to check this characteristic and offer my findings to a group of specialists. I
narrowly escaped excommunication but they advised me to visit a reliable optician urgently.
The characteristic was cherished for years in circles of sulco-friends. But these days even the
most fervent adherents will have recognized that most of the sulcos don’t have hairs behind
the scales on the pericarp, while some weingartias, for example HS 164, do.
Günter Hentzschel (1999) also emended the genus Sulcorebutia. He thought the shape of the
scales on the pericarp to be of major concern. Only the scales of the genera Weingartia and
Gymnocalycium were similar to those of Sulcorebutia.
A second characteristic was the non-branching funicles of Sulcorebutia as opposed to the
plural branching of the two other genera. This suggested a close relationship between
Weingartia and Gymnocalycium.
Alas the observation of the plural branching of funicles in fruits of weingartias turned out to
be an illusion, as was later confirmed by Hentzschel.
Consensus classification
Donald worked on his concept of clines. That’s why he took all plants in the wider
surroundings of Cochabamba to belong to S. steinbachii. It was also part of the spirit of the
times to reduce the number of names. In 1984 Donald participated with the Huntington
Botanical Expedition Bolivia. In his list of fieldnumbers of 1989 still seven varieties of S.
steinbachii were mentioned, namely steinbachii, glomerispina, tuberculato-chrysantha,
gracilior, kimnachii (n.n.), horrida and polymorpha.
According to the Cites Cactaceae Checklist of Hunt (1999) all these names of varieties should
be allowed to expire and in the mean time the name of the genus was changed to Rebutia. A
workgroup of the International Organization for Succulent Plant Study (IUBS-IOS) was
established in 1984 in order to obtain consensus in the classification of the Cactaceae. Some
years later the CITES Plants Committee proposed that the IOS should be supervisor of the
compilation of what was going to be the first edition of the checklist.
Amateurs were confused. How to interpret this list? Some believed, it was only meant for the
use of government customs and excise organisations. Or was it a list with obligatory names
superseding all earlier work? The editors of Succulenta seem to have supported this opinion
for a while.
With unbelieving astonishment circles of amateurs heard that the members of the workgroup
looked for consensus and found it by the raising of hands. Was this science or some pragmatic
acting in which a majority prescribed what names everyone else was allowed to use?
Would somebody dare to doubt the expertise of the members of the work group? The latter
had indeed all won their spurs. It was said about Backeberg that he recognized a not-yet
described plant in an unfamiliar collection immediately. Would all members of the workgroup
have such knowledge at their disposal? Or did they have other skills by which they could
create an acceptable project together?
This question had been answered before, for example by Reto Nyffeler and Urs Eggli (1994).
„The classification of the cacti has been determined during the last decennia to a large extent
by amateurs (persons without basic knowledge of systematic botany) “. This has left deep
traces as a result of which cacti now are in the bad books of scientific botany.

“However many interested amateurs have enlarged the body of knowledge about cacti by their
detailed specific knowledge of forms and by their fieldwork, equally often they have caused
confusion by their lack of knowledge of important biological concepts (evolution, variability,
biology of populations, and so on) and of rigorous working methods.“ 2
Nyffeler and Eggli argued further: “It is the task of systematic botany, to bring about
organisation, in the huge number of plant forms according to the postulated phylogenesis.“
The IOS-workgroup had started with a list of „undisputedly“ accepted genera. For other
genera there was a vote following a discussion. I gladly accept that all members had
significant observations and conclusions at their disposal, which meant their opinions were
valuable. But we do not know these observations and conclusions. Is my question justified, is
a sulcorebutia-specialist automatically qualified to vote about mamillaria? By the way who
supplied the (hypothetical) history of descent? Which method did this person use to collect his
data? Perhaps he used only morphological data.
David Hunt (2006) published the New Cactus Lexicon as a kind of honour to Backeberg. I
can imagine that the „splitter“ Backeberg would have felt somewhat displeased if he had seen
the book. The genera Sulcorebutia and Weingartia had been merged into Rebutia. Hunt
argued, that Rebutia could be seen as a genus of “convenience“. It could possibly be
biphyletic or polyphyletic. I have not the faintest idea what is meant by these two sentences.
The list of names of species was not synonymous with the Cites Checklist. I did not find any
explanation.
In summary dogmas seem to be circulated and have to be followed blindly by allegedly
incompetent people like me. Even if they have real doubts about the postulated relationships.
Sometimes I wondered if Jaap might have been a member of the workgroup.
Also on the level of species we have come across a similar situation. Willi Gertel (1996) for
example mentioned Sulcorebutia steinbachii ssp. tiraquensis var. totorensis subvar.
totorensis. We might hope that this was based on a profound investigation so that this
combination of names would conform to the phylogenesis. But I could not find any
information about what exactly was investigated.
Fig. 11. Sulcorebutia totorensis JK152 Fig. 12. Sulcorebutia jolantana HS 68a
Would it be an argument to see for example S. frankiana as a subspecies of S. steinbachii? I
do not expect much enthusiasm for amateurs putting forward such ideas. But they are inspired
by objective data.
Interesting are comments of L. Ratz in this context. (2005) Can a layman have an opinion
about the method of the botanist? “Botany is a natural science and from this perspective one
can judge when scientific statements are justified according to scientific criteria.“ and further
on: “The basis of all natural scientific investigations are only objective data.“ Obviously Ratz
was not very convinced about the basis for all sorts of comments, concerning the (cactus)
taxonomy.
2 Note: 3 times “knowledge” in one sentence! This must be science.

Some projects
Data, immediately apparent from observing the plant, turned out to lead to shaky conclusions
as you can see from the above remarks. This may be made even clearer by the next example.
A plant in the greenhouse of Karel became 15 cm high. A cutting of this plant which I
received got to only 10 cm. Circumstances and care influence the outward appearance.
Buxbaum had restricted himself to characteristics of flower and seed as these would always
represent „primitive“ characteristics, meaning that the pressure of the environment would
have less effect on them.
A further clarification: if a certain characteristic is found on several plants of the whole group,
it can be interpreted to be „primitive“. It is unlikely that such a characteristic came into being
many times at different places independently of each other.
One can wonder if a characteristic easily changes from one manifestation into another and
afterwards back into the original, creating a kind of blinking light situation. Let us start with a
population, of which all plants have brownish black spines. By a favourable mutation this
population will obtain only white spined plants. But after some generations a next mutation
causes only brownish black spines again.
Nobody will take such a story to be probable but
rather assume that the brownish black spine of
the first population, for example Sulcorebutia
mentosa (Fig. 13), is a primitive characteristic.
Likewise the white spine in the other
population, for example Sulcorebutia albissima
(Fig. 14) will be a primitive characteristic.
There is no known report of a population in
which both forms appear, next to each other. In
the Cites Checklist is S. albissima taken as a
synonym of S. mentosa. By the text above I do
not intend to deny a relationship. I simply cannot
understand the decision to avoid the name
„albissima“. Was this choice purely subjective?
All statements about relationships are based on
probability. Therefore all of them are
hypotheses. One can wonder how to evaluate a
hypothesis when faced with evidence that in
view of the hypothesis is improbable.
Meanwhile the magic word seemed to be DNA,
but this was not a realistic approach for the
common amateur.
In 2004 I was a member of a group of
enthusiastic amateurs who tried to investigate
relationships, using selected isoenzymes. One
can take the characters of these isoenzymes to
Fig. 13. Sulcorebutia mentosa JD175b
Fig. 14. Sulcorebutia albissima JK 39
be primitive. After all, if a mutation is not favourable, there is serious chance, that the
individual with such a mutation will have died because of a failing digestion, before it got
descendants.
The result of comparing of isoenzymes showed that Sulcorebutia is less similar with Rebutia,
but it was not really possible to separate it from Weingartia. Would Brandt be declared right
after all?
Some participants did not appreciate the results of the project very much, perhaps because it
often did not confirm their postulated relationships. Of course one can question the

supposition of actually knowing the correct outcomes in advance. If that were the cases the
interpretation of results may well be biased to confirm such supposition.
Detlev Metzing rejected the results of the project stating that the database was too small.
When I asked him too small for what, he answered with an amiable smile. No, he did not
know the aim, nor had he read the report (Pot 2006).
Afterwards this group of amateurs happened to be able to initiate dna-research. Christiane
Ritz and others (2007) published results based on chloroplast markers: indeed it was not
possible to separate Weingartia and Sulcorebutia. The original group of rebutias from
Argentina and Browningia could be seen as a satelite group of the weingartias. The
relationship with Aylostera, Mediolobivia and Gymnocalycium was shown to be significantly
less strong. Therefore Rebutia minucula and Aylostera pseudominuscula could not belong to
the same genus, contrary to what had been believed for many years. (Fig. 15) Note, that I put
Fig. 15. Cladogram according to Ritz
alternative names, used by amateurs, into the clad gram behind the ones used by Ritz.
Again some people were not fully satisfied with this result. For example how can one
reconcile, that Browningia and Rebutia are that close in the clad gram? Did they suspect a too
small database in this case as well? Or were the browningia samples not very reliable on
further consideration? Or would it have been better to use different markers, assuming that
this was possible?
Gordon Rowley (2009) proposed a genus Rebutia, in which he included the original rebutias,

the weingartias and the sulcorebutias, but not the aylosteras and mediolobivias. It struck me
that he showed only a part of the clad gram of Dr.Ritz, from which the browningias had been
removed.
I don’t know the algorithm behind this clad gram. But in the cladograms prepared by me the
position of every individual is determined by the presence of all other individuals. If a plant is
removed, different arithmetical averages will be found and therefore the position of some of
the plants may change. For the record: the vertical distances in these cladograms have no
other purpose than to keep the diagram legible. Thus they have nothing to do with the
closeness of the relationship.
Ritz stated, that her project confirmed the observation of the branched funicles by Hentzschel.
The same goes for the hairless pericarps of Weingartia, Sulcorebutia and Rebutia. Obviously
the error of Hentzschel had not been discovered and Brederoo and Donald seemed to have
done careless observations.
In my opinion a spicy detail is the names used for species, which would correspond to those
in „Das große Kakteenlexikon“ of Anderson in the case of the rebutias and the sulcorebutias
and to „Die Gattung Weingartia“ of Augustin and Hentzschel in the case of weingartias.
It is reassuring to see that in the clad gram
all canigueralii’s, all neocumingii’s and all
steinbachii’s are close together. The
position of S. cardenasiana did surprise
me.
In the upper part you find a S. spec. (Fig.
16). This might be a very interesting plant,
not only because it is not well known and
wanted. Though it has been discovered at
the same latitude as S. tarijensis, it reminds
one very much of S. cardenasiana. (Fig.
17) Suppose – which I do not suspect of
course – that some error did creep in. In
that case S. cardenasiana would occur
in two different clades. This I would
consider very questionable.
West European amateurs of the continent
prefer to keep old, established names, even
if they are not quite correct. It was a relief
that the „cardenasiana“ mentioned in the
clad gram is called S. langeri every time in
the known collections.
Some amateurs wondered why Ritz did not
immediately recombine all sulcorebutias to
Weingartia. I imagine it was not her
intention at all. Ritz is a geneticist. A
geneticist is not by definition a taxonomist.
Fig. 16. Sulcorebutia spec.
Fig. 17. Sulcorebutia cardenasiana HS 41
By the way, it is not known to me if taxonomist is a recognized profession with a protected
status. Possibly everybody is allowed to call him- or herself a taxonomist.
Günter Hentzschel and Karl Augustin (2008) published the second part of „Die Gattung
Weingartia“. They concluded that morphologically no fundamental differences existed
between Weingartia, Sulcorebutia and Cynthia concerning body, flower and fruit. Also they
had made several attempts to hybridise, between these genera, the results of which could be

considered rather successful, while they had hardly any successful results with other genera.
The consequence of these observations was the recombining of all sulcorebutias to
Weingartia, which had partially been done already by Brandt, about 30 years before.
However some oddities struck me. At page 771 hybrids are shown of S. canigueralii and W.
neocumingii (fa. sucrensis). 14 km from Sucre, along the road to Aiquile, sulcorebutias and
weingartias, usually called canigueralii and neocumingii (fa. sucrensis) as well, grow next to
each other. A natural hybrid was never reported from that place. Should I believe now, that
these plants somehow got the wrong names? Or have canigueralii-populations different
characteristics, by which some will yet hybridise easily with W. neocumingii and others will
not at all?
Hybridising of different species of Weingartia with each other or Sulcorebutia with each other
was not tested by Hentzschel, because „sufficient hybrids by chance already existed in the
collections“. Pip Smart showed me years ago with pride a few hybrids, caused by pollination
on purpose. This had not been an easy result. Johan de Vries and I have the same experience.
(Fig. 18)
I assume the remark about hybrids by chance can easily mislead us. The presence of fruits is
not necessarily evidence of hybridization. This is also well explained by non hybridized
pollination, which is very likely to occur as can be seen by the following. Let us accept that
on a table in the garden there are 100 plants, which all have one and only one partner for
fertilization. Thus on this table exist 50 possible matches. Suppose all plants bloom at the
same time with only one flower, and every flower is equally attractive to a bumblebee. The
insect has landed on a flower. After some time it will ascend and land again. For every flower
the chance that it will land on it is 1 of 100, or 1%. So there is a chance of 99% = 0,99 that the
flower of the match plant is not visited. After a second landing this chance will be 0,99 × 0,99
= 0,99 2 . After a number n landings the chance has become 0,99 n . If n = 459, the chance of no
visit has become less than 1%.
So while it may be true that all sulcorebutias are strongly related, this suggestion has not been
confirmed by observations of fertilization by chance.
Fig. 18. Hybrid of Weingartia fidana (fig. 5) with Sulcorebutia tarijensis JK242

There is still another consideration. If hybridization in nature were that easy, one would not
expect so many strongly differing populations so close together.
The question of relationships motivated me to create a database, which at the moment
contains almost 50 characteristics of 1700 individual plants of the genus Weingartia. Which
characteristics are indeed significant and which are not? From the above we’ve learned that
experts often disagree.
Perhaps the following leads to a sensible choice. A characteristic which is fairly constant for
the whole population can be used for this population, but perhaps not for another one.
Sulcorebutia mentosa for example has magenta flowers, never red or yellow. Thus the colour
of the flower is a significant characteristic in this case. In different populations, which usually
called S. losenickyana all sorts of colours occur. For such populations this characteristic will
not be of much value.
Now I selected plants, similar to the plants in the clad gram of Ritz. I selected characteristics
which can be interpreted as significant for all these plants. In case of the rebutias it was not
possible to check this, as there was only one plant of each species available.
The following characteristics underlie the cladogram (Fig. 19):
position of radial spines distance lower filaments to
pericarp / length pistil
shape of scales on the tube
colour of radial spines length of filament colour perianth in top
structure of surface of radials distance anther to edge colour perianth above upper
perianth
insertions
length radials distance stigma to perianth colour stigma
position central spines diameter of stigma colour filament
shape of the plant body angle tube below insertions colour throat
length of the pistil shape of perianth colour scales on the tube
area of the insertions of
filaments
edge of perianth colour scales on the pericarp
Fig. 19. Cladogram compiled by CactusData
In my estimation both cladograms show a fair
amount of similarity. Of course we should not
forget that the method of Ritz did not
investigate relationships at the level of species,
while my own method is not really meant for
judgements at the level of genera. But after the
critical words of Eggli/Nyffeler and Hunt I take
this result as encouraging.
The key to recognition (Pot 2009) was based on
this database. Last year somebody discovered,
that in this key Sulcorebutia steinbachii was
recognized in different ways, in which
moreover the appearance of the populations
were different. Actually he had chosen to look
for all steinbachii’s in one search operation,
like in the New Cactus Lexicon for example.
According to the NGL a steinbachii is
recognized by: „Body very variable, clustering;
stems depressed-globose; tubercles in circa 13
spirals; central spines 1-3,

almost black; flower c. 3.5 × 3.5 cm; hypanthium well-developed; perianth scarlet to magenta,
rarely yellow, musty-cented; stigma lobes white. “ How many steinbachii’s would be
recognized by Hunt in my collection with these data? How many plants of different species
would he recognize to be steinbachii? Can a steinbachii have yellow spines as well, or an
orange flower, or a lack of central spines? Under which conditions will a sulcorebutia not
correspond to the image of steinbachii? Obviously I do not understand the standards of Hunt.
Nor do I know on what they are based.
How to continue?
Last summer I was visited by a very serious amateur. He confided to me with a serious look,
that he would accept a classification in future only if it had been fully based on dna-research.
Of course I appreciate this very much. But in the meantime I’m a little worried. Until now I
have not heard of any research that will give solutions at the level of species. But suppose it
does happen. Will we, amateurs, be able to do something with it? Will relationships be
confirmed by easily observable characteristics?
Basically they are trying to construct a system based on relationships. But at the same time we
want to know what we are speaking about. DNA-research will be a „black box“ to most of the
cactus amateurs. A solid system, which however is not understood because of obscure
backgrounds has little sense in amateur circles. The same goes for a classification based on
carefully hidden morphological observations.
Maybe Karel was close to the truth when he said: „The only thing that really matters is that
you understand me. Isn’t that right?” Suppose somebody speaks about for example
Sulcorebutia tarabucoensis, which has according to the first description few brown radial
spines, about 8 ribs and red-yellow flowers. But he means a plant with many white radial
spines, about 13 ribs and a magenta flower, from a very different population. My reaction
would be, this person does not know Sulcorebutia tarabucoensis. He for his part perhaps
believes that I do not understand the range of variability of this species. Thus we will not
understand each other.
Professionals have not succeeded in constructing an unequivocal, generally accepted
definition of the concept „species“. How will somebody be able to draw conclusions about the
range of variability of these undefined units? Who will be able to draw conclusions about
strong relationships between such units without defined ranges of variability? Who will be
able to understand that nevertheless, numerous relationships are conjured out of a hat?
I am not a taxonomist. But it is my impression, that empirical experts of the previous century
could not have suspected for a moment the variety of forms of some plant families. People
have found during the last decennia unexpectedly many populations of Weingartia, of which
the majority is well distinguishable from all other populations. Nobody – with or without a
definition of the concept „species“– will expect to recognize a thousand species. But also
nobody is able at the moment to create an understandable and acceptable survey of
relationships in this genus.
Of course one can ignore this multitude of forms. But it does not make any sense to dispose of
all unknown populations as „flowerpot species“. The same goes for accepting all relationships
blindly without supporting data.
Moreover now we are dealing with new modern technology, which may put postulated
relationships in a very different light.
I can easily imagine a Gordian cactus knot, which we will not be able to untangle by
continuing as we have in the past. Yet I keep hoping for new approaches, which will lead us
out of the dilemma. Maybe one day the knot will be untangled in a more sophisticated way
than used by the legendary Alexander. But some splitting may be not avoidable.
People like Nyffeler and Eggli may find my considerations anarchistic. This however is not

my aim. I would welcome an explanation by an expert about the whole area in clear and
workable terms. Maybe this paper will give the initial impetus.
I like to thank Jim Gras for proofreading the English text.
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This article originally written in Dutch by Johan Pot was published in the journal
Succulenta 90:4 (2011) (p. 190 -196) and 90:5 (2011) (p. 227 - 237).
Until today, this English version (translation by Johan Pot) was unpublished.
Published with the permission of the author.