An approximation of a series of seven presentations given during the course of a short visit to the U.S.A. in June 1998.

The title of the talk(s) was given as, “Haworthia, why controversy?”

I have come to the U.S.A. on invitation and the reasons I accepted this invitation are manifold. Primarily I feel a sense of responsibility and duty to the subject, secondly I feel a sense of obligation as my interest in the genus owes much to the USA for the role J R Brown played in stimulating my interests in the genus, and thirdly I felt I ought to dispel the discomfort of the culture shock I had experienced in the USA when I visited it in 1982.

I have wanted to give talks that will in some way enrich the lives of the people who hear them, and this seems to be a very arrogant wish against the limited wisdom which an ordinary individual can acquire about anything in a life-time. But I am concerned about the confusions and controversy, which seems to be associated with the plants I enjoy so much. Classifications and taxonomy have acquired such a negative connotation, and yet they are both fundamental to the whole experience of knowing and growing plants. Without good classification there is no way of organising our thoughts and communicating with one another about the plants.

My interest in Haworthia dates back to my childhood and a deeper interest developed from plants of H. limifolia, which an uncle had collected in Natal. Living in Natal myself, I started to collect plants by corresponding with other collectors and nurseries. It soon became obvious to me that most of the plants seemed to be very ordinarily the same. I was by then a qualified entomologist researching the biology of Noctuid moths, and my study was taking me into the realm of classification and identification which formed the basis of my master’s thesis. My career took a turn and from a government research post I moved to commercial agriculture until fortuitously I landed up as Botanical Assistant to the Curator of the Karoo Botanic Garden in Worcester. There I was given the job of curating collections and given access to the Compton Herbarium and all the Collected Works of G G Smith. I very quickly learned that there was little relation between the available published works on Haworthia and the diversity of the plants I was seeing in the field.

Six years later I could produce a book which was an illustrated checklist of names which I thought could be used to usefully explore the Haworthia further, and also to provide a firmer basis of John Pilbeam’s book on Haworthia and Astroloba. My handbook was revised in 1983 and then in 1985, Col Scott’s book was published which virtually ignored anything which either Pilbeam or I had done. This book seemed to undo any progress which had been made to stable nomenclature in Haworthia and I was very disappointed to find my work categorised with the confusion that collectors have since found themselves in. My conviction is that publishers, editors, other writers, and other collectors whether really serious or not, have simply failed to properly identify the sources of confusion and address them in an ordered way. In my talk I would like to deny any responsibility for any confusion and try to acquire some credibility by pointing out that my work is based on:

1. Extensive fieldwork and thus familiarity with the plants in their native state
2. A knowledge and review of all the literature (I may be the last person who can say I have read all the literature)
3. Extensive experience with pattern recognition in biological systems
4. Knowledge and experience of classification and identification in many plant genera
5. A very comprehensive physical herbarium record located in three different herbaria
6. A clear species definition for the work
7. A long period of validation and testing over a period of 35 years from my first publication on the subject, to the present

When a recent catalogue stated that there was confusion in Haworthia classification, what they were actually doing was confessing their own downright intellectual laziness, and inability to discriminate between writers who are themselves confused and those who are not.

In reading Gould’s book I was also reminded of my childhood belief that the continents of the world had once been joined because they so obviously fitted together. It was interesting to observe that it is only in the last ten years that this hypothesis is accepted as a probable explanation because tectonic plate studies provide an explanation for how this has happened. However, it is the denial of continental drift in the absence of a prior knowledge of this mechanism which is curious to me and I do not think that is science. This has strengthened my view that science is not a matter of education and qualification, profession or position and an impressive CV. It is an attitude which is grounded on common sense and organisation of scepticism.

In order to have this attitude about species, we do need to have a reasonable idea of what a ‘species’ is. Unfortunately science seems to have failed us here as good definition of the term seems either hard to find or impossible to understand and we have to go our own way to do so. Firstly we have to consider that the work should be seen to be a postulate of the biological sciences for a concept of a basic building block for the understanding and classification of all living things in a unified system. Thus it is not for us to hi-jack it, and use to classify things in our individual minds on a basis of limited information, limited material and limited understanding of biological systems, for our own limited purposes.

Unfortunately available definition of the term is poor. The Collins Dictionary defines ‘species’ as those groups into which a genus can be divided, and it then defines ‘genus’ as a group which can be divided into species. The Websters’ Dictionary inserts the work ‘logically’ before ‘divided’. Very few botanical revisions and classifications actually address this question of definition, while on the other hand there seems to be intense intellectual discussion of a biological species concept against other concepts. I cannot see much sense in this. Generally the zoological concept of a species as ‘a group or groups of individuals capable of interbreeding or potentially interbreeding’ is basic to the classification system. This fails in plants because of interfertility across even generic lines. I have simply devised my own definition as ‘a group or groups of individuals interbreeding or potentially interbreeding which vary continuously in space and in time’. This brings us face-to-face with the actual problem of having to determine where these continuities are in space and in time. The problem is that it is the continuities that are obscure and confusing and difficult to describe and circumscribe. Knowing this can make a big difference to how we organise our scepticism about a classification and what we should look for to determine the credibility of writers who can do no better than to confuse themselves and the rest of us.

All too often the view is expressed that classification is an art form and that it expresses the opinions of the individual. If imagination, fantasy and ignorance are the qualifications for the work, then indeed art is what one may get.

In truth classification is and has to be a science in the sense that it has to be based on physical and measurable data. That data has to be accessible to all. Statements must be verifiable and if they are contested, new data should be presented to verify the new and proven statement. This gives rise to a structure of knowledge and information in which the names we use are meaningful and informative. In the case of Haworthia there is a problem (which is not incidentally unique) in that there are very few tangible characters on which classification can be based. Even the characters which differentiate genera in the larger context can be disputed. Therefore, the key to understanding species in Haworthia has to be based on geographic distribution and the spatial relationships and continuities which are observed in the field. Unfortunately again, the strictures of the nomenclatural system and its controls to stabilize names, does sometimes make it a little difficult for the classification to really express how species are related in the field. I have recognised that there is often continuity of varying degree between many different species, and that often I am simply recognising significant nodes in a fairly turbulent sea of similarity. The botanical code requires that names may not necessarily be co-incident with principle nodes. My approach in my first Handbook of 1976 was to try and find as great a relationship between nomenclaturally valid names and the variation in the field. I know I achieved this in very large measure and I have tried to build on that foundation ever since. However, there seems to be no way that the nomenclatural code, whatever its pretensions are to ensuring stability, can do to prevent the structure of the classification from being rattled, shaken and even broken. The onus lies entirely at the door of the individual who should recognise how important it then is for organisation of scepticism.

In my slide presentations, I have pointed out that the genera in the tribe Aloideae of the family Asphodelaceae (following the new dispensation for the classification of plant families by Dahlgren) are not properly understood. What hypotheses have been put forward have been based on some very very poor character definition and analysis. The obvious sub-divisions within the genus Haworthia have been completely ignored and if this is the case I cannot see how any attempt to resort the genus can have any credibility.

I have shown a ‘flow-chart’ showing how the species of the ‘retuse’-type species are linked in a cobweb-like diagram. I pointed out that there are main role players in this web and that the species can be understood in the context of names which relate to geographic centres. My slides were selected to show some of the pathways in and between different centres. This was also to emphasise that a classification has to encompass all plants both known and unknown. In this way there is a predictive element. It is new collections and new methodology which test the classification and its predictions. This process is how an hypothesis is tested and how a classification is shown to be a product of a sceptical and inquiring mind; rather than the artistic product of an individual, driven by some undefined motive underlying a pretension to really understanding what has been done, and what needs to be done.