All living organisms are classified according to a system which was originally developed around 1753 by a Swedish botanist called Carl von Linné. (His name is more commonly seen as Carolus Linnaeus, which is the latinised form of his name.)
The system developed by von Linné is called the Binomial classification system. This consisted of giving each organism a name divided into two parts: the Generic name and the Specific name. Both parts are generally based on the Greek or Latin languages.
In the time of von Linné the number of known Cactus species was only 22, so this was a satisfactory way of describing them. Today the Linnean classification system is still used; however, due to mankind's uncontrollable quest for knowledge, the number and variety of living (and extinct) organisms has increased tremendously. We have now expanded on the Binomial system by adding a varietal name and/or form name. The varietal name (abbreviated to var. or v.) is used to separate members of the same species with slightly different characteristics and the form name (abbreviated to fa. or f.) is used to indicate even smaller differences or to distinguish plants of the same species but from a different locality.
This indicates that the Generic name is Notocactus, the specific name is ottonis, the varietal name is paraguayensis and the form name is Yhaguy Guazu.
Which in plain language means that the plant with that name, is a variety of Notocactus ottonis from Yhaguy Guazu in Paraguay.
When writing about plants from the same genus the normal convention is to use the full generic name the first time it is written and for subsequent occurrences only the initial is used. For example if we are talking about the genus Weingartia, eg. Weingartia neocumingii, the first time the name comes up we use the full name and after that the form W. neocumingii is used.
However, what one person only considers to be a variety or form of a certain plant, another person may believe to be a separate species or even a genus. So this can lead to the same plant having different names depending on its origin.
Both of these names refer to the same plant, but which one you use depends on whether you are a lumper or splitter. A lumper groups similar looking plants together and a splitter "splits" different looking plants and gives them separate names. As there are no universally accepted definitions of what constitutes a genus, species, variety or form, there can be various degrees of lumping and splitting. You can go from the ultimate (I hope !!) in lumping adopted by the IOS Consensus, in which the genus Notocactus has been lumped in with the genus Parodia, to over zealous splitting, where every slightly different plant is given a new name.
I believe that we must have some way of distinguishing between different taxa. The number of Notocactus species, for example, is too large and many of our plants should be reduced to varieties or forms, but these different taxa must be distinguished, in some form or another, so that we don't get inadvertent hybridization between them. Whether this is achieved by distinguishing differences by use of form names or just identifying them by use of collection numbers, I leave up to the Notocactus experts.
The name of a species can give some idea of what it looks like. But because the names are written in Latin it can seem a bit confusing at first, so a Latin dictionary of biological terms may be of some use to unravel the meaning of a name.
The generic name Notocactus is derived from the Greek words "Notos" meaning south and "Kaktos" meaning a type of thistle, indicating that members of this genus are Cacti that originate in the South (America).
The specific name will sometimes gives some idea of the morphology of a particular plant,
This specific name is composed of two parts: "nigri-" meaning "black" and "-spinus" meaning "spines". So this is a Notocactus with black spines, simple !
After a while a pattern may be seen when looking at the end phrase of a name. The specific name of many of our plants end in the same suffix:
If you read the Cactus literature, you will often see the name of a person after the plants name,
This name indicates that this plant was originally described by Albert F.H. Buining. There is sometimes an additional form as well,
this indicates that the plant was described first by two people called Link and Otto, but its name was later revised by Van Vliet.
In fact, this plant was first described as Echinocactus orthacanthus Link et Otto by Link and Otto, in 1827, when most globular Cacti were called Echinocactus. Latter, in 1954, it was moved into the genus Malacocarpus, by Herter, to become Malacocarpus orthacanthus (Link et Otto) Herter and then more recently was renamed again, in 1970, as Notocactus orthacanthus by Van Vliet, when the genus Malacocarpus was reduced to a subgenus of Notocactus.
As you can see, only the original and most recent authors names are listed.
There are also some other strange words added to the ends of names. Most of these relate to aspects of the plants name. They are:
This form indicates this plant is a hybrid between Notocactus herteri and N. uebelmannianus. The convention is that the female parent plant is listed first followed by the male. Which in this case means the seed was set on plant of N. herteri which was pollenated by N. uebelmannianus.
This is the form used for naturally occurring hybrids, in this case between T. laui and T. pseudopectinatus.