Question

from when the law of priority was in vogue​

Answer 1

Answer:

The principle of priority has not always been in place. When Carl Linnaeus laid the foundations of modern nomenclature, he offered no recognition of prior names. The botanists who followed him were just as willing to overturn Linnaeus's names. The first sign of recognition of priority came in 1813, when A. P. de Candolle laid out some principles of good nomenclatural practice.  

Priority is a fundamental principle of modern botanical nomenclature and zoological nomenclature. Essentially, it is the principle of recognising the first valid application of a name to a plant or animal. There are two aspects to this:

The first formal scientific name given to a plant or animal taxon shall be the name that is to be used, called the valid name in zoology and correct name in botany.

Once a name has been used, no subsequent publication of that name for another taxon shall be valid (zoology) or validly published (botany).