Different authors have used different systems of nomenclature over the years. The following is an attempt to make sense of systems which are currently in use. Contributors to the APS quarterly periodical Primroses may find the following notes useful.
1. The botanical family is always capitalized: Primulaceae (Be careful of the spelling!)
2. The botanical genus is capitalised: Primula (See Halda1) or Primula (See Richards2).
3. The section is capitalised: section Soldanelloides / section Muscarioides / section Crystallophlomis / etc. It is not usually put in italics.
4. The genus name is always italicised (Primula) when it is used as the first word in a species' two-part name (the binomial system). See #5 below.
5. The species and subspecies names are given in italics (or underlined if italic type is not available).
6. The species name and the subspecies name which may follow it are entirely in lower case. There is no upper case initial letter, even when the species is named after a person or a place: Primula sieboldii (after Count von Siebold); Primula bhutanica (after the country of Bhutan).
7. The full species name (Genus species) should be used at its first mention in a text. Thereafter, the genus part (the first word) can be abbreviated to its initial letter (G. species): "We found Primula vialii growing in an alpine bog. We had never seen P. vialii in the wild before..." This also applies if mention of a different species of the same genus follows in the text: " Primula auricula and P. hirsuta are known to hybridize in the wild." The species name is not used in isolation: "I love vialii." " I notice that hirsuta has sticky hairs on its leaves." (Of course, we do this when we speak!)
8. The subspecies name follows the species name. It can be shown in more than one way. For example,
a) preceded with subsp. (Richards): Primula vulgaris subsp. sibthorpii
b) preceded with ssp. (Halda): Primula vulgaris ssp. sibthorpii
After the first mention, the first two parts of the full name of the subspecies can be dropped to subsp. or ssp. For example: "The dwarf Primula elatior subsp. leucophylla and the lovely purple subsp. meyeri are worthy garden plants."
[For purposes of the APS Quarterly it makes sense to use the shorter ssp. without italics, to be consistent with var. (variety) and f. (form), which are not usually italicized.]
9. Hybrids (crosses), both natural and man-made, are shown with X. The symbol is not italicised. Use a capital X for clarity: "The hybrid P. verticillata X P. floribunda is known as Primula X kewensis and is probably self-fertile."
10. The word for a named variety or cultivar should be given in single inverted commas, without italics. A cultivar, which is a choice form of a species (i.e., unhybridized), is given without X: "It is difficult to find good examples of Primula japonica 'Postford White' these days." / "My wife has a plant of the old cultivar P. allionii 'Mrs Dyas'." When the named variety is the result of deliberate or natural hybridizing, the symbol X is used: "The hybrid Primula X 'Johanna' is a deliberate hybrid of P. warshenewskiana and P. clarkei, though it resembles P. rosea. It was named after the hybridizer's daughter."
11. Use the word primulas (no capital letter, no italics, can be singular or plural) when you do not mean the scientific genus, but are describing these plants in general. This word covers species, garden cultivars and natural or garden hybrids. (See Richards, page 8, line 1, and page 9, line 9). "My mother used to grow a wide variety of primulas, including many species of the genus Primula such as Primula japonica." Similarly, we can say "I love all kinds of anemones, especially the white wood anemone, Anemone nemorosa" or "I grow many modern varieties of roses, but my favourite is still Rosa eglanteria, the wild eglantine."
12. Note that the three websites of the National Auricula and Primula Society (NAPS) in the UK seem to prefer a capital 'A' for exhibition auriculas, along with capitalization for all parts of the names of show plants: Green Edged Auriculas, Gold Centred Alpine Auriculas, Light Centred Alpine Auriculas, Double Auriculas, Show Auriculas, Show Selfs, Gold Laced Polyanthus.
13. It is necessary to distinguish between 'alpine and 'Alpine'. For example, "At the show there were far more Alpine Auriculas than any other class of Auriculas." This makes it clear that you do not mean plants which actually grow in alpine regions. Compare this with the following, in which the geographic distribution is meant: "The species Primula auricula is an alpine or subalpine plant from central Europe, whereas Primula palinuri grows on coastal cliffs in southern Italy."