Re: Why is the second word in a scientific name not capitalized?

Originally, there were no scientific names for individual species. Each separate species was given a description in Latin. The description was a sentence. The first word in the sentence, following Latin grammar, was the generic name of the organism. As the first word in a sentence, the generic name was always capitalized.

For example, a common European rose, now widely known as the "wild briar rose" was named: Rosa sylvestris inodora seu canina. My latin is very rusty but a rough translation might be: "Rose of woodlands without fragrance (and something about dogs, perhaps 'like a dog', as in 'mean', a reference to the many prickles on the briar-like stem). By the middle of the eighteenth century, this system had become very cumbersome, especially given the flood new species that were being discovered in parts of the world being explored by Europeans.

In 1753, Carl Linnaeus, also known as Carl von Linné or Carolus Linnaeus (generally referred to simply as Linnaeus), published a now famous review of the current status of plant species. Linnaeus named his work Species Plantarum. This publication marks the beginning of modern taxonomy.

For each species he covered in this monumental work, Linnaeus took one word from the description and placed it in the margin of the text. This practice was not new with Linnaeus, other early botanists had done it before. However, Linnaeus was the first one to do it uniformly for every species he published in Species Plantarum. This fact, together with the wide and authoritative influence of Species Plantarum, gave the binomial (two name) method a tremendous advantage. It is still the system used today.

The marginal name came to be called the trivial name or the epithet. All scientific names now consist of the generic name followed by the specific epithet. Reference to the epithet as the "species name" is erroneous, as the name of any species is the binomial. All binomials are treated as Latin words and, hence, italicized in English text.

To get back to your question, the epithet is, in origin, a single word taken from a polynomial description, which was originally a sentence. So, following the trend set by Linnaeus in 1753, we continue to use a lower case initial for the epithet. Incidentally, for the "wild briar rose" Linnaeus used the word 'cania' as the marginal word. Hence Rosa canina, the dog rose.