The species is the basic unit that we divide living things into and originally species were seen as clearly distinct from one another. What puzzled scientist was how species appeared in the first place? The answer was species evolved from other species as a result of a battle for survival; as carefully argued in Charles Darwin’s “On the Origin of Species by Means of natural Selection or, The Preservation of Favoured Races in the Struggle for Life”. As is often the case the answer to this question produced a second question; if species appear as the result of a gradual change from one species into a second, where does one species stop and the next start. This argument will keep taxonomist in work so long as there are species to classify!

Clearly this makes a precise definition of what a species is impossible and whether a plant belongs in a separate species to another is the result of a consensus being formed. This consensus though is not fixed and has to be open to debate.

Species is also the basic unit of plant and animal scientific names and the name of a species is the combination of both the genus and species names. The rules for how a species name is structured is defined by International Code of Nomenclature for algae, fungi, and plants (as it is now known) and this goes into great details; but some of the important rules are:

• With in any genus no two species can have the same name or one that could cause confusion with others.
• For plants; the species name cannot be the same as the genus it belongs in, unlike animal names. So Rattus rattus, the black rat, is a valid name for an animal but the style would be unacceptable for a plant.
• Importantly the species is always begun with a lower case letter,
• The genus should be written immediately before it (the genus can be abbreviated to its first letter if it does not risk causing confusion) and both the genus and species should be in italics or if not practical underlined.