I have not been very visible since 1983 and I need to try and explain why I am here.

It is by your invitation and at your expense, and frankly I wonder at my arrogance at assuming that I can meet the implications of this invitation.  I felt uncomfortable here (in USA) in 1981, especially at Albuquerque where my impression was that the audience wanted an entertainer and a performer.
I cannot fill that role.

Nevertheless, I am deeply conscious that I have some kind of debt and responsibility to you.  I am anxious to hold your respect and your affection – and to have some credibility when it comes to the real subject of my talk, hoping of course that it will impress itself upon your minds.

My role in Haworthia is this.  I grew up with J.R. Brown’s Succulents for the Amateur as my picture book.  I have been familiar with Haworthia since 1940 when I first started to grow them.  I tried to collect them seriously when I lived in Natal, but what I could obtain all looked very alike to me.  It is only when I landed up at the Karoo Botanic Garden that I began to understand the problem.

Classification really is a very important function and collection is barely possible without it.  It is not perchance that books on genera stimulate collecting frenzies.  Classification helps us organise our thoughts and experience and helps us communicate with one another.  At its lowest level it may only provide a list of collectable objects.

The view is constantly being propagated that classification is a matter of opinion and that it is not a science but an art form.  Prior to Darwin it seemed that nature was simply a product of a divine creative event and nobody really thought about the relationship of plants and animals to one another.  Darwin changed all that by suggesting that species were related to each other in a way that could be understood in a rational way by the collection and analysis of data.  From then on everyone started to dabble in classification.  What we forget is that classification of plants is a huge structure designed and refined to accommodate all living organisms.

The species is the basic building block and it is a postulate of biological science – it is not a concept we can hi-jack to organise our individual thoughts from limited material, limited experience and from a blinkered viewpoint.

It is ironic that there are two aspects of Darwin’s theory we seem to ignore:-

1. He conceived a system of slow and gradual change, whereas we tend to see plants as all at the same stage of change and definition frozen like that in time.

2. He conceived species as having evolved from earlier simpler forms, and we tend to suggest that there was less variability in these parental organisms than in whatever has evolved from them.

In 1991 there was an article in the British Cactus and Succulent Journal which claimed that in spite of the fact that there were now three books on Haworthia, there was still confusion about the classification. Then I recently saw an Abbey Garden catalogue which also complained about confusion in Haworthia.

Now, for the last twenty years I have felt like a rat trapped in a corner.  Constantly having to refute what other people write, or defend my own intellectual integrity from shallow thoughts of this kind.

This myth of confusion (and it is and will be a myth if you will only follow what I say) is a huge and painful disappointment to me.  I think there has been a near total failure on the part of editors, writers, reviewers and otherwise more interested and knowledgeable collectors, to properly identify the sources of confusion and avoid them.

It has been really humiliating to have my work categorised as confusing when I have tried so conscientiously and honestly to explain what the position is with the diffidence and reservation that is an integral part of my nature.
What I would like you to know that my work is based upon:-

1. A thorough knowledge and experience with the variability, distribution and identification of many plant genera.
2. Extensive experience and training in pattern recognition in biological systems.
3. Extensive field work.
4. A knowledge and review of all the less trivial literature on Haworthia.
5. A very comprehensive physical herbarium record in three different herbaria and specimens arranged according to my system of classification.
6. A clear species concept and definition on which the classification is based.

The classification in the classical way is also constructed to account for all haworthias now known, as well as for those not known.  It therefore has a large predictive element.

During the last 15 years, this classification has been tested and re-tested with both re-collections and new collections.  This has resulted in a book currently being printed and hopefully available soon.

When anyone says that the nomenclature is confused, my contention is that they are simply confessing their own intellectual indolence, their own indecisiveness, their own ignorance and their own personal state of mind.  They consequently cannot discriminate between writers who are confused and those who are not.  A classification has to stand on data which can be analyzed and synthesised, added to and moulded into an hypothesis built on a firm foundation.  There also has to be some agreement on how this is done and also some definition of the terms that are used.

It has been said that “the ship of many a taxonomist has been wrecked on the rocks of the Liliaceae”.  I was warned of this in 1970, have been constantly aware of it, and have navigated a very deliberate and careful course.

I have derived a species definition that is a lot better than those generally used and also a lot better than the dictionary definition.  My definition for a biological species is this:-

“A group or groups of organisms which interbreed or have the potential to interbreed, and these organisms vary continuously both genetically and morphologically in space and time.”

But there are three constraints beyond those of human fallibility:-

1. The discontinuities in Haworthia (but definitely not only in Haworthia) are often obscure and difficult to describe and circumscribe.
2. To quote Stephen Gould “The strongest statement that a scientist can make is ‘hardly ever'”.
3. Again Gould “The chimera of certainty is for politicians and preachers”.

Classification can be presented as an art form which is simply a product of individual imagination, fantasy and ego; or as a product of objective thought and examination based on data, hypotheses, testing and review all under the principle of organised scepticism.

It is actually very easy to see the difference.